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THE LIBRARIES 


COLUMBIA UNIVERSITY 


AVERY LIBRARY 


A 


MANUAL 


OF THE PRINCIPAL 


USED IN 
American Engineering and Surveying, 


MANUFACTURED BY 


Wiecé oy Eb. GURLEY. 


REVISED EDITION. 


2 Eo 


TRO YS NG Ae: 
PUBLISHED BY W. & L. E. GURLEY. 
1856. 


. 


Entered according to Act of Congress, in the year 1855, 


7 he | BY W. &L. E GURLEY, 


In the Clerk’s Office of the District Court for the Northern Dit 
New York. % ; 


* 


“ + >> 


D. H. Jones & oo Poivrans, 
Troy, ING We 


PRICK LIST 


ee 
i TS insirumenis 
\ 
' i : vine] ) no Sh 
COMPASSES. 
Plain, with Jacob Staff mountings, 4 inch needle, Acasa ation iced oe $20,00 
zs a Opti ae Want tede amapta tie sags 25,00 
he sf us ne 3 6 BY ESS ctopticcos seadog 28,00 
‘Vernier, cS we se Guess SOR LS a aieinin ste chee 50 35,00 
Rail Road, “ € f 5} “ clo aus oundelau ene 55,00 
EXTRAS. 
Compass DB RIDO WIC OUETEN LAP G rc watt oerS s/is to oyctenteaegiia's baie aa a 932 5,00 
“« with lev’g screws and Clamp and Tang’t movem't, 12,00 
“ce “é “c ““e +6 without & “ce 6 “6 10, 00 
REMI POT UPA cea c5 ys i's Pelle wc ow delta Se os ate wns ele oe 4,00 
TRANSITS. 
Vernier, plain telescope * 6 inch needle, with compass tripod,.... 60,00 
Sur veyors’ : 5 54 “ if ACI USHUC TUM acm O0SO0 
Engineers’ “ " light, 4 inch needle, a “tote? aves eae O00 
“<é “6 ““ heavy, pt ** se “6 “ see 125,00 
s ‘“« - with watch+telescope,.......... 150,00 
“e ss Cee theodoliteraxishan acts cele 150,00 
$6 os “~ two telescopes,........+-. 190,00 
EXTRAS, 
Vertical circle, 34 in, diameter, vernier reading to five minutes, 5,00 
6< 4“ 44 “e “a “ce “ec single 66 10,00 
Clamp and Tangent movement to axis of telescope,...........-. 5,00 
Level on Telescope, with ground bubble and scale,...........-. 10,00 
Rack and pinion movement to eye glass... 1... ee eee ce wees 5,00 
Sights on telescope with folding joints,.......-....ccsseescecee 5,00 
cs “ Standards at right angles to telescope,............. ea LOGO) 


*A “plain” telescope is ene without any of the attachments, as the 
elamp and tangent, vertical circle and level. 


wo 


PRICE LIST. 


LEVELING INSTRUMENTS. 


Sixteen inch telescope, with adjusting tripod,. . Sane rae . $96,00 
Eighteen “ BET tia) ae Seay eS” © Ria +s vil gts bee - 90,00 
Twenty ‘ & 08 a es + bau eee eee sean ee 0,00 
Twenty-two a a ce e6 Soe MP sco to 90,00 
Farm level, ce fc us ff). Bah sen .. 40,00 
Builders’ level, “ a is EA a Me ey wees 0100 
LEVELING RODS 
Yankee. (Or BOstOnss.2., oss. 0'us 01s e wis 5. ave, 01.6 » oye ocsi0.e, 0 Ae ee 12,00 
New York, with improved mountings,.............. eri I RUU 
CHAIN 
100 feet, with oval rings, No. 5 wire, 6th Bor aewnre eo Ane 7.50 
i ai eh Ke ae Ok te Se! nee oat tse aan ss 6,00 
50 “* xe a se OE ae EOS ec. Cir. apres seecane 4,00 
ee ae a Hy CO RR ee eR Ain 4 A ets em 3,50 
6G)“ SP TOUI C Micswl MERC Ol! Micki esc ette bre «0 ae a fer 3,00 
SO hee Me - 4 a i ir Peer A os se 1,76 
6m td eCmmestOcl AVIRA ah nts vctne wire Clee vic oa tee big 5,00 
338 CS Pg we ra ss he’) lek tis cinch Grane ’ +: wie eae 2,75 
Set 10 marking Pins,.. ROTC. RO ONE nh Ne 2 5 ae 16 
MEASURING TAPES. 

Chestermanis. steel, "88 feet... sctaceies aele Satele > efeea ae eee 7,50 
ae < BOM Saget eres .ere bie (aa late og Mere. aiele eee eee 11,50 

oe > OF nena te clos he AA on on . 14,50 

SS 1. OV) apc) atts Bes Siena ptals..< tovatelas A's tps cmceiaiele nomena 20.00 

CCL MVOEATIO ME BS Si5 (ok praise leis one bps ss 1s eheuk, ee oe ee 7 2.50 

ee s DOV ois a occarepo its ot Rivet ates anim PG. 0 Sic 3,00 

% fe CO ateereletere tere tere A At Ris are 3,25 

Ay ss (Soe OME Wey ts a eee Cire scr ine orate PPROIE oto 3 3,50 

Ke fe NO oak aio. ot ccs fees wee see ter tas aet rae eae aug ae oe Be CaS 

os 8 SU ele mic che la/stlelic. eens orapie 06 + wie eres eee 4,00 

4 ce UOUN My SaRiae 5 oh ole 56 Biphe ue eerete Sueusae 5,00 


POCKET COMPASSES. 


With folding sights, 24 inch needle, very serviceable for retracing 


“ce ce 
ce 6e 
«“c ce 


Without sights, 


73 s 
“e at 
“ 

1 to 2 


lines once surveyed,......... 6,00 

is with jacob staff mountings,.. 7,50 
‘“ “ ‘ “ “ 9,00 
ee « without ss ¢: 8,00 
$6 cs bch dhe ae eee oe from 25 ets. to 2,50 
6,00 


Miners’ Compasses, for tracing iron ore,.. aes ss ale + «nate 


For prices of Drawing Instruments, separate or in cases, refer to the 
Supplement to our Manual. 


° eer 


{Information to Purchasers. 


Instruments Wantep.—In regard to the best kind of instruments for 
particular purposes, we would here say, that where only common survey- 
ing, or the bearing of lines in the surveys for county maps is required, a 
Plain Compass is all that is necessary. In cases where the variation of 
the needle is to be allowed, as in running over the lines of an old farm, or 
the surveys of Government lands, the Vernier Compass, or the Vernier 
Transit, is required, 

Where, in addition to the variation of the needle, horizontal angles are 
to be taken, in cases of local attraction, the Rail Road Compass is prefer- 
able; and for a mixed practice of surveying and engineering, we consider 
the Surveyors’ Transit superior to any other instrument made by us or 
any other manufacturers. 

Where Engineering is the exclusive design, the Engineers’ Transit and 
the Leveling Instruments are of course indispensable. 

The Farm and Builders’ Levels, are intended for laying out mill seats 
and determining the levels of buildings in course of erection. 

Warranty.—All our instruments are examined and tested by us in per- 
son, and are sent to the purchaser adjusted and ready for immediate use. 

They are warranted correct in all their parts—we agreeing in the event 
of any defect appearing after reasonable use, to repair or replace with a 
new and perfect instrument, promptly and at our own cost, express 
charges included, or we will refund the money and the express charges 
paid by him. 

Packine, &c.—Each instrument is packed in a well finished mahogany 
case, furnished with lock and key and brass hooks, the larger ones having 
besides these a leather strap for convenience in carrying. Each case is 
provided with screw-drivers, adjusting pin, and wrench for centre pin, 
and if accompanied by a tripod, with a brass plumb-bob; with all instru- 
ments for taking angles, without the needle, a reading microscope is also 
furnished. 


Ay INFORMATION TO PURCHASERS. 


Unless the purchaser is already supplied, each instrument is accompa- 
nied with our ‘‘ Manual,” giving full instructions for such adjustments and 
repairs as are possible, to one not provided with the facilities of an instru- 
ment maker. 

When sent to the purchaser, the mahogany Gases are carefully inclosed 
in outside packing boxes, of pine, made a little larger on all sides to allow 
the introduction of elastie material, and so effectually are our instruments 
protected by these precautions, that of several thousand sent out by us 
during the last twelve years, in all seasons, by every mode of transporta- 
tion, and to all parts of the Union, and the Canadas, not more than three 
or four have sustained serious injury. 

Means or Transportation.—Instruments can be sent by Express to 
almost every town in the United States and Canadas, regular agents being 
located at all the more important points, by whom they are forwarded to 
smaller places by stage. The charges of transportation from Troy to the 
purchaser are in all cases to be born by him, we guaranteeing the safe 
arrival of our instruments to the extent of express transportation, and 
holding the express Companies responsible to us for all losses or damages 
on the way. 

Terms or Payment are uniformly cash, and we have but one price, 
Our prices for instruments are nearly one-third less than those of other 
makers of established reputation. They are as low as we think instru- 
ments of equal quality can be made, and will not be varied from the list 
given on the previous pages. 

Remittances may be made by a draft payable to our order at Troy, 
Albany, New York, Boston, or Philadelphia, which can be procured from 
Banks or Bankers in almost all of the larger villages. 

These may be sent by mail with the order for the instrument, and if lost 
or stolen en the route, can be replaced by a duplicate draft obtained as 
before, and without additional cost. 

Or the customer may pay the bill on receipt of the instrument to the 
express agent, taking care to send funds bankable in New York or Boston. 

All persons ordering instruments by mail, or by proxy, may rely on 
receiving as perfect and cheaply as if ordered in person. 


W. & L. E. GURLEY, 


Mathematical Instrument Makers, 


Futon Sr., opposite Unton R. R. Depot, Troy, N. Y, 


ERRATUM. 


On page 11, six lines from bottom, in directions for 


‘e-magnetizing the needle, for “ corresponding,” read 


o 


yp posite poles of the ms monet. 


PREFACE. 


In offering this little work to the public, the publishers have designed 
to supply a want which an experience of many years in the manufacture 
of Instruments, as well as practice in the field, has taught them, is very 
generally felt by American Surveyors and Engineers. 

The various Instruments employed in English and European practice 
are so different from those preferréd by the great majority of American 
Engineers, that no description of the former, however excellent, is applica- 
ble to such as are manufactured and used in our own country. 

The entire absence of any treatise upon American Instruments, as well 
as the numerous inquiries which are made by our business correspondents, 
has led us to believe that a Manual, furnishing a full deseription of the 
peculiarities and adjustments of those manufactured at our establishment, 
would be acceptable, not only to our own customers, but to the. profession 
generally. 

With the hope, therefore, that our little book may enable the Engineer 
and Surveyor to understand their Instruments, and discover and rectify 
any derangement in their adjustments, or injury from ordinary accidents, 

we now commit it to the indulgence of those for whom it has been 
_ designed. 
W. & L, E. GURLEY. 
Troy, May 1, 1856. 


™ 


SURVEYING INSTRUMENTS. 


THe various instruments used in Surveying may be conve- 
niently arranged, into two general divisions. 

(1.) Neeptx instruments,—or such as owe their accuracy aud 
value to the magnetic needle only, embracing the Plain and Ver- 
nier Compasses, and ihe Vernier Transit. 

(2.) ANGULAR instruments, including those in which the hor 
zontal angles, are measured by a divided circle and verniers, a 
well as by-the needle also; as the Rail Road Compass, the Su 
veyor’s and Engineer’s Transits, &c. 

In the present work we shall consider first, those imstruments 
comprised in the first division, and; as in these the accuracy of 
the horizontal angles indicated, depends upon the delicacy of the 
needle, and the constancy with which it assumes a certain direc 
tion, termed the “magnetic meridian,” we shall here remarl 
briefly upon, the form, the dength, and the movement of the mag. 
netic needle, : 

The forms of the needle are almost infinitely varied according 
to the taste or fancy of the maker or surveyor, but may be re- 
solved into two general classes, one having the greatest breadth 
in a horizontal, the other-in a vertical direction. 

We have usually made our needles about one twentieth of an 
inch broad and one third as thick, parallel from end to end, the 
north and south poles being distinguished from each other, by a 
small scollop on the north end. 

The length of the needle varies in different instruments, from 
four to six or even seven inches, those of five and a half, or six 
inches long, being generally preferred by surveyors. 

1* 


6 SURVEYING INSTRUMENTS. 


The movement of the needle, with the least possible friction, is 
secured by suspending it, by a jewelled centre upon a hardened 
steel pivot, the point of which is made perfectly sharp and 
smooth. - 

The test of the delicacy of a magnetic needle is the number of 
horizontal vibrations, which it will make in a certain are, before 
coming to rest—besides this, most surveyors prefer also to see a 
sort of quivering motion in a vertical direction. 

This quality which is manifested more in a horizontal, than in 
a vertical needle and depends upon the near coincidence of the point 
of suspension, with the centre of gravity of the needle, serves to 
show merely, that the cap below is unobstructed. 

Having now considered the different qualities of a good needle, we 


shall proceed to speak of those instruments of which it makes 
so important a part; of these the most simple is that termed the 


PLAIN COMPASS. 
Fig. 1. 


i 
Raa LTT (OTA Ts ri 
ET 


Too 


enim 

4 

— 

—— 
i 


As represented above, the Plain Compass, has, a needle six 


JL ke tents 


e 8 hy 


THE PLAIN COMPASS. 7 


inches long, a graduated circle, main plate, levels, and sights, 


and is placed upon the brass head of the ‘Jacob staff.” 


Tur Compass Crrcre, in this, as in all our instruments, is di- 
vided to half degrees on its upper surface, the whole degree 
marks being also cut down on the inside circumference, and is fig- 
ured from 0 to 90, on each side of the centre or “line of zeros.” 

The circle and face of the compass are silvered. 


Tue Sprrit Levens are placed at right angles to each other 
so as to level the plate in all directions, and are balanced, upon a 
pivot in the middle of the tube so as to be adjustable by a com- 
mon screw-driver. 

Tue Siaurs, or standards, have fine slits cut through nearly 
their whole length, terminated at intervals by large circular aper- 
tures, through which the object sighted upon is more readily 
found. Sometimes a fine horse-hair or wire is substituted for one 
half the slote, and placed alternately with it on opposite sights. 


Tancent Scare.—The right and left hand edges of the sights 
of our compasses, have respectively an eye-piece, and a series of 
divisions, by which angles of elevation and depression, for a range 
of about twenty degrees each way, can be taken with considera- 
ble accuracy. 

Such an arrangement is very properly termed a “ tangent 
scale,” the divided edges of the north sight, being tangents to 
seoments of circles having their centres at the eye-pieces, and 
their points of contact with the tangent lines at the zero divisions 
of the scale. 

The cut shows the eye-piece and divisions for angles of de- 
pression ; those for angles of elevation, concealed in this cut, are 
seen in that of the Railroad Compass. 

Tue Jacos Starr mountings which are furnished with all our 
compasses, and packed in the same case, consist of the brass head 
already mentioned, and an iron ferule or shoe pointed with steel 
so as to be set firmly in the grouud. 


& THE PLAIN COMPASS. 


The staff to which the mountings should be well fitted and 
driven on is procured from any wheelright, or selected by the sur- 
veyor himself, from a sapling of the forest. 


To Adjust the Compass. 


Tue Levers. — First bring the bubbles into the centre, 
by the pressure of the hand on different parts of the plate, 
and then turn the compass half way around; should the bubbles 
run to the end of the tubes it would indicate that those ends 
were the highest; lower them by tightening the screws immedi- 
ately under, and loosening those under_the lowest end until by 
estimation the error is half removed; level the plate again, and 
repeat the first operation, until the bubbles will remain in the 
centre, during an entire revolution of the compass. 

Tue Sigurs may next be tested by observing, through 
the shits, a fine hair or thread made exactly vertical by a plumb. 
Should the hair appear on one side of the slit the sight must be 
adjusted by filmg off its under surface on that side which seemed’ 
the highest. 

THe NEEDLE is adjusted in the following manner :—Haying the 
eye nearly in the same plane with the graduated rim of the com- 
pass circle, with a small splinter of wood, or a slender iron wire, 
bring one end of the needle in line with any prominent division 
of the circle, as the zero, or ninety degree mark, and notice if the 
other end corresponds with the degree on the opposite side ; if it 
does, the needle is said to “cut” opposite degrees; if not, bend 
the centre-pin by applying a small brass wrench, furnished with 
our compasses, about one-eighth of an inch below the point of 
the pin, until the ends of the needle are brought into line with 
the opposite degrees. 

Then holding the needle in the same position, turn the com- 
pass half way around, and note whether it now cuts opposite de- 


THE PLAIN COMPASS. 9 


grees. If not, correct half the error, by bending the needle, and 
the remainder by bending the centre-pin. 

The operation should be repeated until perfect reversion is se- 
cured in this first position. 

This being obtained, it may be tried on another quarter of the , 
circle ; if any error is there manifested, the correction must be 
made in the centre-pin only, the needle being already straighten- 
ed by the previous operation. 

When again made to cut, it should be tried on the other quar: 
ters of the circle, and corrections made in the same manner until 
the error is entirely removed, and the needle will reverse in every 
point of the divided surface. 


To use the Compass. 


In using the Compass the Surveyor should keep the south end 
towards his person, and read the bearings from the north end of 
the needle. He will observe that the EE and W letters on the 
face of the compass are reversed from their natural position, in 
order that the direction of the line of sight may be correctly read. 

The compass circle being graduated to half degrees, a little 
practice will enable the surveyor to read the bearings to quar- 
ters, or even finer—estimating with his eye the space bisected by 
the point of the needle, and as this is as low as the Traverse ta- 
ble is usually calculated, it is the general practice. 

Sometimes, however, a small vernier is placed upon the south 
end of the needle, and reads the circle to five minutes of a de- 
gree—the circle being in that case graduated to whole degrees. 

This contrivance, however, is quite objectionable on account 
of the additional weight imposed on the centre-pin, and the diffi- 
culty of reading a vernier which is in constant vibration, and is 
therefore but little used. 


To Taxes AnaLes or Exevation.—Having first leveled the 
compass, bring the south end towards you, and place the eye at 


10 THE PLAIN COMPASS. 


the little button, or eye-piece, on the right side of the south sight, 
and with the hand fix a card on the front surface of the north 
sight, so that its top edge will be at right-angles to the divided 
edge, and coincide with the zero mark; then sighting over the 
top of the card, note upon a flag-staff the height cut by the lme 
of sight; then move the staff up the elevation, and carry the 
ecard along the sight until the line of sight again cuts the same 
height on the staff, read off the degrees and half degrees passed 
over by the card, and we shall have the angle required. 


For ANGLES oF Depression.—Proceed in the same manner, 
using the eye-piece and divisions on the opposite sides of the 
sights, and reading from the top of the standards. 

The compass is furnished with a ball spindle, or socket, upon 
which it turns, and by which it is leveled. The ball may be 

placed in a single or ‘jacob staff” socket, as represented in the 
figure, or in a compass tripod, such as is shown im the cut of the 
Vernier Transit beyond. 

In the side of the hollow cylinder, or socket, of the compass 
which fits to the ball spindle, is a screw by which the instru- 
ment may be clamped to the spindle in any position. 


Besides the clamp screw, we have recently fitted to the sockets 
of our compasses a little spring catch, which, as soon as the in- 
strument is set upon the spindle, shps into a groove and thus re- 
moves all danger of falling when the instrument is carfied. 


There is also underneath the mam plate a needle-lifting screw, 
which, by moving a concealed spring, raises the needle from the 
pivot, and thus prevents the blunting of the point im transpor- 
tation. 

When the compass is not in use it is the practice of many 
Surveyors to let down the needle upon the point of the centre- 
pin, and let it assume its position in the magnetic meridian so as 
to retain or even increase its polarity. 

We would advise in addition, that after the needle has settled 


\ 


THE PLAIN COMPASS. tt 


it should be raised against the glass, in order not to dull the point 
of suspension. 

A little caution is necessary in handling the compass, that the 
glass covering be not excited by the friction of cloth, silk, or the 
hand, so as to attract the needle to its under surface. 

A brass cover is sometimes fitted over the glass as a precau- 
tion against disturbances of this kind. 

When, however, the glass becomes electric, the fluid may be 
removed by breathing upon it, or touching different points of its 
surface with the moistened finger. 

An ignorance of this apparently trifling matter has caused 
many errors and perplexities in the practice of the inexperienced 
Surveyor. 

Repairs of the Compass. 


To enable the Surveyor to make such repairs as are possible 
without having recourse to an instrument maker, we here add a 
few simple directions. 

1. Toe Nerepie.—It may sometimes happen that the needle 
has lost its polarity, and needs to be re-magnetized ; this is effect- 
ed in the following manner : 

The operator being provided with an ordinary permanent mag- 
net,* and holding it before him, should pass with a gentle pres- 
sure each end of the needle from centre to extremity over the 
magnetic pole, describing before each pass a circle of about six 
inches radius, to which the surface of the pole is tangent, draw- 
ing the needle towards him, and taking care that the north and 
south ends are applied to the corresponding poles of the magnet. 

Should the needle be returned ina path near the magnetic 
pole, the current induced by the contact of. the needle and mag- 
net in the pass above described, would be reversed, and thus the 
magnetic virtue almost entirely neutralized at each operation. 

When the needle has been passed about twenty-five times in 


* A magnet suitable for this purpose costs from 12 to 25 cents, 


12 THE PLAIN COMPASS. 


succession, in the manner above described, it may be considered 
as fully charged. a 

A fine brass wire is wound .in two or three coils on the south 
end of the needle, and niay be moved back or forth, in order to 
counterpoise the varying weight of the north end. 


2, Tum Centre-Pin.—This should occasionally be examined, 
and if much dulled, taken out with the brass wrench, already _ 
spoken of, or with a pair of plyers, and sharpened on a hard 
oil stone —the operator placing it in the end of a small stem of 
wood, or a pin vice, and delicately twirling it with the fingers as 
he moves it back and forth at an angle of about 45° to the 
surface of the stone. 

When the point is thus made so fine and sharp as to. be invisi- 
ble to the eye, it should be smoathed by rubbing it on the surface 
of a soft and clean piece of leather. 


3. To pur In 4 New Guass.—Unscrew the “bezzle ring ” 
which holds it, take out the little brass ring and the old glass, and 
scrape out the putty; then if the new glass does not fit, smooth 
off its edges by holding it obliquely on the surface of a grind-stone, 
until it will enter the ring easily ; then put im new putty, spring 
in the brass ring, and the operation will be completed. 

4, To REPLACE A Sprrit Levert.—Take out the screws which 
hold it on the plate, pull off the brass ends of the tube, and with 
a knife-blade, scrape out the plaster from the tube; then with 
a stick, made a little smaller than the diameter of the tube, 
and with its end hollowed out, so that it will bear only on the 
broad surface of the level vial, push out the old vial, and replace 
it with a new one, taking care that the crowning side, which is 
usually marked with a file on the end of the vial, is placed on the 


upper side, 

When the vial does not fit the tube it must be wedged up by 
putting under little shps of paper until it moves in snugly. 

After the vial is in its place, put around its end a little boiled 


THE PLAIN COMPASS. 13 


plaster, mixed with water to the consistency of putty, taking 
care not to allow any to cover the little tip of the glass, then 
slip in the brass ends, and the operation will be completed. 

We would here remark that an extra glass and level vials are 
always furnished, free of charge, with our instruments whenever 
desired by the purchaser. 


Sizes of the Plain Compass. 


Three different sizes of this instrument are in common use — 
having respectively four, five, and six inch needles, and differing 
also in the length of the main plate, which in the four inch Com- 
pass is twelve and a half inches long, and in the larger sizes 
fifteen and a half inches. 

The six inch needle compass is generally preferred. 

The Plain Compass, which was the only one in use in this 
country previous to the time of David Rittenhouse, has grad- 
ually given way to the superior advantages of the Vernier or 
Rittenhouse Compass, which we shall now proceed to describe. 

2 


SURVEYING INSTRUMENTS. 


THE VERNIER COMPASS. 
Fig. 2. 


The Vernier Compass, represented in fig. 2, differs from the 
instrument just described, in having its compass circle with a 
vernier attached, movable about a common centre, by turning the 
‘tangent screw,” seen at the south end of the plate. 

The superiority of the Vernier over the Plain Compass consists 
in its adaptation to the retracing the lines of an old survey, and 
in the surveys of the U.S. public lands, where the lines are based 
on a true meridian. 


THE VERNIER COMPASS. 15 


Variation of the Needle. 


It is well known that the magnetic needle, in almost all parts 
of the United States, points more or less to the east or west of 
a true meridian; or north and south line. 

_ This deviation, which is called the Varration or Drciina- 
TION of the needle, is not constant, but increases or decreases to 
a very sensible amount in a series of years. 

Thus at Troy, N. Y., a line bearing m 1830, N. 31° E. would 
now, 1856, with the same needle, have a bearing of about N. 
32° K., the needle having thus in that interval, traveled a full 
degree to the west. 

For this reason, therefore, in running over the lines of a farm 
from field notes of some years standing, the Surveyor would he 
obliged to make an allowance, both perplexing and uncertain, in 
the bearing of every line. : 

To avoid this difficulty the vernier was devised, the arrange- 
ment of which we shall now describe. 


Tur VERNIER is divided on its edge to thirty equal parts and 
figured in two series on each side of the centre. 

In the same plane with the vernier is an-.arc or limb, fixed to 
the main plate of the compass, and graduated to half degrees. 

The surfaces of both vernier and limb are silvered. 

On the vernier are thirty equal divisions, which exactly cor- 
respond in length with twenty-nine of the half degrees of the 
limb. 

Each division of the vernier, is therefore, one-thirtieth, or, in 
other words, one minute longer than a single division of the limb. 


To Reap THE VERNIER.—In “reading” the vernier, if it is 
moyed to the right, count the minutes from’its zero point to the 
left, and vice versa. Proceed thus until a division on the vernier 
is found exactly in line with another on the limb, and the lower 
row of figures on the vernier will give the number of minutes pas- 
sed over, When the vernier is moved more than fifteen minutes 


16 THE VERNIER COMPASS. 


to either side, the number of the additional minutes up to thirty 
or one-half degree of the limb is given by the upper row of figures 
on the opposite side of the vernier. 

To read beyond thirty, add the minutes given by the vernier 
to that number, and the sum will be the correct reading. 

In all cases when the zero point of the vernier passes a whole 
degree of the limb, this must be added to the minutes, in order 
to define the distance over which the vernier has been moved. 


To TURN OFF THE V ARIATION.—It will now be seen, that the 
Surveyor having the Vernier Compass, can by moving the vernier 
to either side, and with it of course the compass circle attached, 
set the compass to any variation. 

He therefore places his instrument on some well defined line 
of the old survey, and turns the tangent screw until the needle 
of his compass indicates the same bearing as that given in the 
old field notes of the original survey. 

Then screwing up the clamp screw underneath the vernier, he 
can run all the other lines from the old field notes without further 
alteration. 

The reading of the vernier on the limb in such a case, would 
give the change of variation at the two different periods. 

The variation of the needle at any place being known, a true 
meridian, or north and south line, may be run by moving the 
vernier to either side, as the variation is east or west, until the 
are passed over on the limb is equal to the angle of variation; 
and then turning the compass until the needle is made to cut the 
zeros on the divided circle, when the line of the sights would 
give the direction of the true meridian of the place. 

Such a change in the position of the vernier is always necessary 
in surveying U. 8. public lands, which are always run from the 
true meridian. 

“THE LINE OF NO VARIATION,” as it is called, or that upon 
which the needle will indicate a true north and south direction, is 
situated in the United States, nearly in an imaginary line drawn 


THE VERNIER COMPASS. 1? 


from the middle of lake Erie to cape Hatteras, on the coast of 
North Carolina. 

A Compass needle, therefore, placed east of this line, would 
have a variation to the west, and when placed west of the line, 
the variation would be to the east, and in both cases the varia- 
tion would increase as the needle was carried farther from the 
line of no variation. 

Thus in Minnesota the variation is from 15° to 16° to the east, 
while in Maine it is from 17° to 18° to the west. 

At Troy, in the present year, 1856, the variation is about 7° 
44’ to the west, and is increasing in the same ¢lirection from two 
to three minutes annually, 

To Reap to Minutrs.—A less important use of the vernier 
is to give a reading of the needle to single minutes, which is ob- 
tained as follows: 

First be sure, as in all observations, that the zero of the ver- 
nier exactly corresponds with that of the limb; then noting the 
number of whole degrees given by the needle, move back the 
compass circle with the tangent screw until the nearest whole de- 
eree mark is made to coincide with the point of the needle, read 
the vernier as before described, and this. reading, added to the 
whole degrees, will give the bearing to minutes. 


To Use the Vernier Compass. 


Proceed in the same manner as directed in regard to the Plain 
Compass, when making new surveys, always taking care that 
the vernier is set at zero and securely clamped by screwing up 
the nut beneath the plate. 

In surveying old farms, allowance and correction must be made 
for the variation, as just described. 


Sizes of the Vernier Compass. 


We make but one size of this instrument, having a six inch 
needle and a main plate fifteen and a half inches long. 
The adjustments of the Vernier Compass are mainly those of 
the instrument first described, and need not here be repeated. 
2% , 


SURVEYING INSTRUMENTS. 


THE VERNIER TRANSIT. 
Fig. 3. 


\\ \ \ 

\ 

vn 
The Vernier Transit or Transit Compass, represented in the 

cut above, has the same general properties as the Vernier Com- 

pass, but is furnished with a telescope in place of the ordinary 


sights. 


i 


f 


—CO£ES Sef 


THE VERNIER TRANSIT. 19 


The telescope is from ten to twelve inches 
long, and sufficiently powerful to see and set 
a flag at a distance of two miles, in a clear 
day. 

The cross bar in which it is fixed, turns 
readily in the standards, so that the telescope 
can be turned in either direction, and back 
and fore sights be taken without removing 
the instrument. 

Like all telescopes used by us in our in- 
struments, it shows objects in an erect po- 
sition. 


Tur TrLescopr.—The interior construc: 
tion of the telescope of the Vernier Transit 
which is very similar to those of the other 
instruments we shall describe, is well shown 
zin the longitudinal section represented in 
e fig. 4. 

As here seen, the telescope consists essen- 
tially of an object-glass, an eye-piece tube, 
and a cross-wire ring, or diaphragm. 

The object-glass is composed of two lens- 
es, one of flint, the other of crown glass, 
which are so made and disposed, as to show 
the object seen through it without color or 
distortion. 

The object-glass, and the whole Telescope 
is therefore said to be “achromatic.” 

The eye-piece is made up of four plano- 
convex lenses, which, beginning at the eye 
end, and proceeding on, are called, respect: 
ively, the eye, the field, the amplifying, and 
the object lenses. 


20 THE VERNIER TRANSIT. 


Together, they form a compound microscope, magnifying the 
minute image of any object formed at the cross wires by the in- 
terposition of the object-glass. 


Fig. 5. 


Tur Cross Wires.—The cross-wire diaphragm, two views of 
which are here exhibited, is a small ring of brass, suspended in 
the tube of the telescope by four capstan head screws, which 
press upon the washers shown on the outside of the tube. 


The ring can thus be moved in either direction, by working 
the screws with an ordinary adjusting pin. 

Across the flat surface of the ring two fine fibres of spider’s 
web are extended at right angles to'each other, their ends bemg 


cemented with bee’s wax, or varnish, into fine lines cut in the 


metal of the ring. 

The intersection of the wires forms a very minute point, which, 
when they are adjusted, determines the optical axis of the tel- 
escope, and enables the Surveyor to fix it upon an object with 
the greatest precission. 

The imaginary line passing through the optical axis of the 
telescope, is termed the “line of collimation,” and the operation 
of bringing the intersection of the wires into the optical axis, is 


i dhe 


THE VERNIER TRANSIT. xt 


called the ‘adjustment of the line of collimation.” This will be 
hereafter described. 

The openings in the telescope tube are made considerably 
larger than the screws, so that when these are loosened, the 
_ whole ring can be turned around for a short distance in either 
direction. 

The object of this will be seen more plainly, when we describe 
the means by which the wire is made truly vertical. 

The sectional view of the Telescope (fig. 4,) also shows two 
moveable rings, one placed at A A, the other at C C, which are 
respectively used, to effect thé centering of the eye-piece, and the 
adjustment of the object-glass slide. 

The centering of the eye-tube is performed after the wires have 
been adjusted, and is effected by moving the ring, by means of 
the screws, shown on the outside of the tube, until the intersec- 
tion of the wires is brought into the centre of the field of view. 

The adjustment of the object slide, which will be fully described 
in our account of the Leveling Instrument, secures the movement 
of the object glass in a straight line, and thus keeps the line of 
collimation in adjustment through the whole range of the slide, 
preventing at the same time what is termed the “traveling” of 
the wires. 

This adjustment, which is peculiar to our telescopes, is always 
made in the process of construction, and needing no further at- 
tention at the hands of the Engineer, is concealed within the hol- 
low ball of the telescope axis. 


Optical Principles of the Telescope. 


In order that the advantages gained by the use of the tele- 
scope may be more fully understood, we shall here venture briefly 
to consider the optical principles involved in its construction. 

We are said to “see” objects because the rays of light which 
proceed from all their parts, after passing through the pupil of the 
eye, are by the crystalline lens and vitreous humor, converged 


22 THE VERNIER TRANSIT. 


to a focus on the retina, where they form a very minute inverted 
image; an impression of which is conveyed to the brain by the 
optic nerve. 

The rays proceeding from the extremities of an object, and 
crossing at the optic centre of the eye, form the “visual angle,” 
or that under which the object is seen. 

The apparent magnitude of objects depends on the size of the 
visual angle which they subtend, and this being great or small, 
as the object is near or distant—the objects will appear large or 
small, in an inverse proportion to the distances which separate 
them from the observer. 

Fig, 6. Thus, (in fig. 6, ) if 
the distance O A is one- 
half of O B, the visual 
Bangle, subtended by the 
object at the point A, 
and therefore the appa- 
rent magnitude of the 


rH 


s= 


object will be twice that observed at B. If, therefore, the visual 
angle subtended by any object, can be made by any means twice 
as large, the same effect will be produced as if the observer were 
moved up over one-half the intervening distance. 

Now this is the principal advantage gained in the use of a 
telescope. 

The object-glass receiving the rays of light which proceed from 
all the points of a visible object, converges them to a focus at the 
cross wires, and there forms a minute, inverted, and very bright 
image, which may be seen by placing a piece of ground glass to 
receive it at that pot. 

The eye-piece acting as a compound microscope, magnifies this 
image, restores it to its natural position, and conveys it to the eye. 

The visual angle which the image there subtends, is as many 
times greater than that which would be formed without the use of 
the telescope, as the number which expresses its magnifying power. 


Fig. 7. 


THE VERNIER TRANSIT. Zo 


Thus, a telescope which magnifies twenty times, 
increases the visual angle just as: much, and 
therefore diminishes the apparent distance of the 
object twenty times—or in other words, it will 
show an object two hundred feet distant, with the 
same distinctness, as if it was distant only ten feet 
from the naked eye. 

The accompanying cut, (fig. 7,) which we are 
kindly permitted to copy from an excellent treatise 
on surveying, by Prof. Gillespie of Union College, 
will give a correct idea of the manner in which 
the rays of light coming from an object are 
affected, by passing through the several glasses of 
a telescope. ; 

We shall only consider the rays which proceed 


from the extremities ; 


; these after passing through 


the object-glass, here shown as a single lens, are 
conveyed to the point B, the centre of the cross 
wires and the common focus of the object and 
eye glasses. At this place the rays crd&8s each 
other and the image is inverted. 

The rays next come to the object lens C, and 
passing through it are refracted so as again to 
cross each other, and come thus to the amplifying 
lens D. By this they are again refracted, made 
more nearly parellel and thus reach the large field 
lens H. After passing through this, they form a 
magnified and erect image in the focus of the eye 
lens G. By the eye lens the image is still further 
magnified, and at last enters the eye of the ob- 
server, subtending an angle as much greater than 
that at the point O, as is the magnifying power of 
the telescope. 

In place of the eye-piece of four lenses, which 


24. THE VERNIER TRANSIT. 


we have just been considering, and which is exclusively used in 


oO) 

all American instruments made at the present day; another, 
which has but three lenses, is often seen in the telescopes of im- 
ported instruments. 

This latter, which inverts the object, hana saving a little 
more light than the former, is exceedingly troublesome to the in+ 
experienced observer, and has never been popular in American 
Engineering. 

To ascertain the Magnifying Power of a Telescope. 

Set up the instrument about twenty or thirty feet from the 
side of a white wooden house, and observe through the telescope 
the space covered by one of the boards in the field of the glass; 
then, still keeping that eye on the Telescope, hold open the other 
with the finger, if necessary, and look with it at the same object. 
By steady and and careful observation there will be seen on the 
surface of the magnified board, a number of smaller ones seen by 
the naked eye, count these and we shall obtain the magnifying 
power. 

If the limits of the magnified board, as seen through the 
telescope, can be noted so as to be remembered after the eye is 
removed, the-number of boards contained in this space may then 
be easily counted. 

The side of an unpainted brick wall, or any other surface, con- 
taining a number of small, well marked and equal objects, may be 
observed, in place of the surface we have described. 

The operation described requires great care and close-observa- 
tion, but may be performed with facility after a little practice. 

We have spoken of the effect of the telescope in magnifying 
obiestsy but have not mentioned what is termed its “ illuminating 
power.” 

This arises from the great diameter, or aperture of the object- 
glass, compared with that of the pupil of the eye, which enables 
the observer to intercept many more rays of light, and bring the 
object to the eye highly illuminated. 


THE VERNIER TRANSIT. Ao 


The advantage gained in this increase of light depends, as is 

evident, on the size of the object-glass, and the perfection with 
which the lenses transmit the heht without absorbing or reflect- 
ing it. 
_ The superficial magnifying power of a telescope, is found by 
squaring the number which expresses its linear magnifying power ; 
thus a telescope which magnifies twenty times, increases the sur- 
face of an object four hundred times. 

Before an observation is made with the telescope, the eye- 
piece should be moved in or out, until the wires appear distinct 
to the eye of the operator; the object-glass is then adjusted by 
turning the pinion head until the object is seen clear and well 
defined, and the wires appear as if fastened to its surface. 

The intersection of the wires, being the means by which the 
optical axis of the telescope is defined, should be brought pre- 
cisely upon the centre of the object to which the instrument is 
directed. 

Having thus briefly considered the principles, we will now pro- 
ceed to describe the 

- Attachments of the Telescope. 

A telescope is said to be “plain” when it is without any ap- 
pendages to its tube or axis, and most instruments are made in 
that manner. 

Many surveyors, however, prefer to add these conveniences, 
and we shall now consider them in detail: 

CLAmp AND Tancent.—This consists essentially of a ring, en- 
circling the axis of the telescope, and having two projecting 
arms, the one above being slit through the middle and holding 
the clamp screw, the other much longer and below, is connected with 
the tangent screw. 

As soon as the clamp screw is tightened, the ring is brought 
firmly around the axis, and the telescope can then be moved up 
or down by turning the tangent screw. 

The clamp and tangent ought always to accompany the vertical 


circle and the level on the telescope. 
3 


26 THE VERNIER TRANSIT. 


VerticaL Circte.—A divided circle, as seen in the cut of the 
Vernier Transit, is often attached to the axis of the telescope, 
giving, with a vernier, the means of measuring vertical angles, 
with great facility. 

We make two sizes of these circles, one of staat 3 1-2 inches 
diameter, seen with this instrument, the other an inch larger, and 
shown in the cut of the Engineer’s Transit. The former is gra- 
duated to single degrees, and reads, by the vernier, to five minutes 
of adegree. The latter, divided to half degrees, gives a reading, 
with the vernier, to single minutes. 

The vertical circle is fitted firmly to the telescope axis, and 
fastened with a screw, so that it remains permanent. 

The vernier however, may be shifted in either direction, by 
loosening the screws which confine it to the standards. 

The vernier of the small circle is divided into twelve equal 
parts, which correspond with thirteen degrees on the circle. 


Each division of the vernier 1s, therefore, one-twelfth of onc 
degree, or five minutes longer than a single division of the circle 
so that the angles are read to five minutes of a degree. 


The vernier is double, having its zero point in the middle, an — 
the reading up to thirty minutes, is said to be direct: that is, if th 
circle is moved to the right, the minutes are read off on the righ 
side of the vernier, and vice versa, 

The minutes beyond thirty are obtained on the opposite side, 
and in the lower row of figures, 

By following these directions, and noticing the first divisions on 
the circle and vernier, which exactly correspond, the surveyor can 
obtain a reading to five minutes, with great facility. 


LeveL ON TEeLEscope.—Besides the vertical circle, there is 
sometimes a small level attached to the telescope of this, and 
other instruments, which we shall hereafter describe. 


Such an attachment is shown in the cut of the Surveying Tran- 


sit, and its adjustment and advantages will be explained in our ac: 
count of that instrument. 


THE VERNIER TRANSIT. 27 


Sieuts on TeLescore.—We are sometimes desired by survey- 
ors, to place a pair of short sights on the upper side of the tele- 
scope tube. 

They are best made to fold close to the tube, when not in use, 
sike- those of the pocket compass, described hereafter. 

These sights are thought to be useful in taking back sights 
without turning the telescope, and in sighting through bushes or 
in the forest. 

We believe, however, that a telescope is incomparably better, 
in every situation, and would never advise their construction 
or use, 

Sicuts ror hiaur Ancies.—Besides the sights just mentioned, 
we have often attached others to the plate of the instrument, on 
either side of the compass circle, or on the standards. 

These being adjusted to the telescope, give a very ready means 
of laying off right angles, or running out offsetts, without chang- 
ing the position of the instrument. 

To Adjust the Vernier Transit. 

TuE Levens of this instrument have a capstan head screw at 
each end, and are adjusted with a steel pin in the same manner as 
those of the Vernier Compass. 

Tur NerEDLE is adjusted as described in our account of the 
Plain Compass. 

Line or Couitimation.—To make this adjustment, which is, in 
other words, to brmg the intersection of the wires into the optical 
axis of the telescope, so that the instrument, when placed in the 
middle of a straight line will, by the revolution of the Telescope, 
cut its extremities—proceed as follows: 

Set the instrument firmly on the ground and level it carefully ; 
and then having brought the wires into the focus of the eye- 
piece, adjust the object glass on some well defined point, as the 
edge of a chimney, or other object, at a distance of from two to 
five hundred feet; determine if the vertical wire is plumb, by 
clamping the instrument firmly to the spindle and applying the 


28 THE VERNIER TRANSIT. 


wire to the vertical edge of a building, or observing if it will 

“move parallel to a point taken a little to one side; should any de- 
viation be manifested, loosen the cross wire screws, and by the 
pressure of the hand on the heads outside the tube, moye the 
ring around until the error is corrected. 

The wires being thus made respectively horizontal and vertical, 
fix their point of intersection on the object selected; clamp the 
instrument to the spindle, and having revolved the telescope, find 
or place some good object in the opposite direction, and at about 
the same distance from the instrument as the first object assumed. 

Great care should always be taken im turning the telescope, 
that the position of the instrument upon the spindle is not in the 
slightest degree disturbed. 

Now, having found or placed an object which the vertical wire 
bisects, unclamp the imstrument, turn it half way around, and 
direct the telescope to the first ohject selected; having bisected 
this with the wires, again clamp the instrument, revolve the Tele- 
scope, and note if the vertical wire bisects the second object 
observed. 

Should this happen, it will indicate that the wires are in adjust- 
ment, and the points bisected, are with the centre of the instru- 
ment, in dhe same straight line. 

If not, however, the space which separates the wires from the 
second point observed, will be double the deviation of that point 
from a true straight line, which may be conceived as drawn 
through the first point and the centre of the instrument, since the 
error is the result of two observations, made with the wires when 
they are out of the optical axis of the telescope. 


Fig. 8. 


For as in the diagram, let A represent the centre of the instru- 


THE VERNIER TRANSIT. 29 


ment, and B C the imaginary straight line, upon the extremities of 
which the line of collimation is to be adjusted. 

B represents the object first selected, and D the point which the 
wires bisected, when the telescope was made to revolve. 

When the instrument is turned half around, and the telescope 
again directed to B, and once more revolved, the wires will bisect 
an object, H, situated as far to one side of the true line as the point 
D is on the other side. 

The space, D H, is therefore the sum of two deviations of the 
wires from a true straight line, and the error is made very appa- 
rent. 

In order to correct it, use the two capstan head screws on the 
sides of the telescope, these being the ones which affect the po- 
sition of the vertical wire. 

Remember that the eye-piece inverts the position of the wires, 
and therefore, that in loosening one of the screws, and tightening 
the other on the opposite side, the operator must proceed as if to 
increase the error observed. Having in this manner moved back 
the vertical wire until, by estimation one quarter of the space, D E, 
has been passed over, return the instrument to the point B, revolve 
the telescope, and if the correction has been carefully made, the 
wires will now bisect a point, C, situated midway between D and 
j, and in the prolongation of the imaginary line, passing through 
the point B and the centre of the instrument. 

To ascertain if such is the case, turn the instrument. half 
around, fix the telescope upon B, clamp to the spindle, and 
again revolve the telescope towards ©. If the wires again 
bisect it, it will prove that they are in adjustment, and that the 
points B, A, C, all lie in the same straight line. 

Should the vertical wire strike to one side of C, the error must 
be corrected precisely as above described, until it is entirely 
removed. 

Another method of adjusting the line of collimation, often 


employed in situations where no good points in opposite directions 
3% 


30 THE VERNIER TRANSIT. 


can be selected upon which to reverse the wires may here be 
described. 

The operator sets up the instrument in some position which 
commands a long sight in the same direction, and having 
leveled his instrument, clamps to the spindle, and with the 
telescope locates three points which we will term A, B, and 
CG, which are distant from the instrument about one, two, and 
three hundred feet, respectively. 

These points, which are usually determined by driving a 
nail into a wooden stake set firmly into the ground, will all 
lie in the same straight line however much the wires are out 
of adjustment, since the position of the instrument remains 
unchanged during the whole operation. 

Having fixed these points, he now moves the instrument to 
B, and sets its centre directly over the nail head, by lettmg down 
upon it the point of a plumb-bob suspended from the tripod. 

Then having leveled the instrument, he directs the wires to A, 
clamps to the spindle, and revolves the telescope towards C. 
Should the wires strike the nail at that point, 1t would show that 
they were in adjustment. 

Should any deviation be observed, the operator must correct 
it by moving the wire with the screws until, by estimation, 
half the error is removed, 

Then bringing the telescope again upon either A or C, and 
revolving it, he will find that the wires will strike the point 
in the opposite direction, if the proper correction has been 
applied. 

If not, repeat the operation until the telescope will exactly cut 
the two opposite points, when the intersection of the wires will be 
in the optical axis, and the line of collimation in adjustment. 

In our description of the previous operation, we have spoken 
more particularly of the vertical wire, because in a revolving 
telescope this occupies the most important place, the horizontal 
one being employed mainly to define the centre of the vertical 


THE VERNIER TRANSIT. 31 


wire, so that it may be moved either up or down without 
materially disturbing the line of collimation. 

The wires being adjusted, their intersection may now be brought 
into the centre of the field of view. 

Tur Hyr-pixce, is centred by moving the screws A A, shown 
in the sectional view of the telescope Fig. 4, which are slackened 
and tightened in pairs, the movement being now direct, until 
the wires are seen in their proper position, 

It is here proper to observe that the position of the line of 
collimation depends upon that of the object-glass, solely, so 
that the eye-piece may, as in the case just described, be moved 
im any direction, or even entirely removed and a new one 
substituted, without at all deranging the adjustment of the 
wires. 

Tue Stranparps.—In order that the wires may trace a 
vertical line as the telescope is moved up or down it is necessary 
that both the standards of the telescope should be of precisely 
the same height. 

To ascertain this and make the correction if needed, proceed as 
follows: : 

Having the line of collimation previously adjusted, set the 
instrument in a position where points of observation, such as the 
point and base of~ a lofty spire, can be selected, giving a long 
range in a vertical direction. 

Level the instrument, fix the wires on the top of the object, 
and clamp to the spindle; then bring the telescope down, until 
the wires bisect some good point, either found, or marked at the 
base ; turn the instrument half around, fix the wires on the 
lower point, clamp to the spindle, and raise the telescope 
to the highest object. 

If the wires bisect it, the vertical adjustment is effected; if 
they are thrown to either side, this would prove that the standard 
opposite that side, was the highest, the apparent error being 
double that actually due to this cause. 


82 THE VERNIER TRANSIT. 


To correct it, we now make one of the bearings of the axis 
movable, so that by turning a screw underneath this sliding piece 
as wellas the screws which hold on the cap of the standard, the 
adjustment is made with the utmost precision, 

This arrangement which is common to all our telescope imstru- 
ments is very substantial and easily managed. 

Tur VERTICAL CIRCLE.— W hen this attachment requires adjust- 
ment proceed by leveling the instrument carefully, and having 
brought into line the zeros of the wheel and vernier find, or 
place some well defined point, or line, which is cut by the 
horizontal wire. 

Turn the instrument half around, revolve the telescope, and 
fixing the wire upon the same point as before, note if the zeros 
are again in line. 

If not, loosen the screws, and move the zero of the vernier 
over half the error; bring the zeros again into coincidence, and 
proceed precisely as at first described, until the error is entirely 
corrected, when the adjustment will be completed. 

Should it be desired, at any time, the circle can be removed 
by the surveyor, and replaced at pleasure. 

Tur Leven on TELescopre.—The adjustment of this will 
be best considered when we come to speak of the Surveyors 
Transit. 

ADJUSTMENTS IN GENERAL.—We ought here to say that 
the above adjustments, as well as all the others which we have 
previously explained or may hereafter describe, are always made 
by us in person, but are given in this work in order that the, 
Surveyor and Engineer may fully understand their instruments 
and be enabled to detect and remedy errors and accidents which 
in practice will often occur. 


To Use the Vernier Transit. 


This instrument is used on the ordinary ball and spindle 
placed most commonly in the compass tripod as shown in Fig, 3. 


THE VERNIER TRANSIT. 83 


Trirop Hrap.—Sometimes leveling screws with the parallel 
plates, and which together we shall designate the “tripod head” 
with a clamp and tangent movement, are used with this 
instrument as well as with the Surveyors Transit. 

This tripod head can be unscrewed from the legs, and is 
packed in the instrument box ; it is of very moderate cost, 
and in almost every situation is infinitely superior to a_ ball 
and socket support. 

Ban AND Socker.—This we also make in all cases where the 
tripod head is furnished by cutting a screw upon the lower end of 
the jacob staff, a ball and spindle being also supplied so that the 
Surveyor can use the same instrument either upon a jacob staff, 
a compass tripod, or a leveling tripod. 


Compounp Bati.—We also manufacture 
what may be termed a “compound ball 
spindle,” which has a tangent movement, 
and gives all the perfection of more costly 
arrangements, with a very moderate expense. 

As represented in the cut, it has an inte- 


rior spindle, around which an outside hollow 
cylinder is moved, by turning the double- 


headed tangent screw, which has in the mid- 


dle, an endless screw, working into teeth, cut 


spirally around in a groove of the cylinder. 
The compass, or other instrument, revolves 


on the outside socket, precisely as if placed 
(Fig. 9.] on a common ball spindle; but when a 
slower movement is required, can be made fast by the clamp 
screw, and then turned gradually around the interior spindle, by 
the tangent screw, until the slote of the sight, or the intersection 
of the wires, is made to bisect the object with the utmost cer- 
tainty. 
‘The compound ball may be placed either in a jacob-staff socket, 
or compass tripod. 


84 THE VERNIER TRANSIT. 


Tue Spring Carcau, described in our account of the Plain 
Compass, is always attached to the socket of this instrument, 
whether placed upon a ball or tripod, so that jt cannot slip off 
from the spindle in carrying. 

THE Ciamp Screw, in the side of the secleat of this instru- 
ment, is shown in Fig. 3, and by pressing a brass spring in the in- 
terior against the spindle, serves to fix the instrument in any 
position, 

THe VeRNIER is moved by the tangent screw, now always, 
placed above the plate, precisely as described in our account of 
the Vernier Compass, and is read to minutes in the same manner, 

There is also a clamp nut underneath the vernier by which it 
is securely fixed in any position, which must be loosened whenever 
the vernier is moved by the tangent screw. 

Tur Nerpie Lirtina Screw is the same as those of the 
compasses previously described. 

In SurveYING with this instrument, the operator proceeds pre- 
cisely as with the Vernier Compass, keeping the south end to- 
wards his person, reading the bearings of lines from the north end 
of the needle, and using the telescope in place of sights, revolving 
it as objects are selected in opposite directions. 

Parattax.—Before an observation is made with the telescope, 
the eye-piece should be moved in or out until the wires appear 
distinct to the eye of the operator ; the object glass may then be 
placed in position, by turning the pinion head on the top of the 
telescope until the object is seen clear and well defined, and the 
wires appear as if fastened to its surface. 

When on the contrary, the wires are not perfectly visible, the 
observer by moving his eye to either side of the small aperture of 
the eye-piece will cause the wires to “travel” on the object, and 
thus occasion what is termed the “error of parallax.” 

The intersection of the wires being the means by which the 
optical axis of the telescopes is defined, should be brought pre- 
cisely upon the centre of the object to which the mstrument is 
directed. 


THE VERNIER TRANSIT. 85 


To Take ANGLES or ELevation.—Level the instrument care- 
fully, fix the zeros of the circle and vernier in line, and note the 
height cut upon the staff or other object by the horizontal wire ; 
then carry the staff up the elevation, fix the wire again upon the 
same point, and the angle of elevation will be read off by the vernier. 

By careful usage, the adjustments of the vernier transit will 
remain as permanent as those of the ordinary compass, the only 
one liable to derangement, being that of the line of collimation. 

This should be examined occasionally, and corrected in the 
manner previously described. 


Repairs of the Vernier Transit. 


These being in great part already spoken of, it will be neces- 
sary to consider only such as belong to the telescope. 

To RepLace THE Cross Wires.—Take out the eye-piece tube, 
together with the little rmg by which it is centered, and having 
removed two opposite cross wire screws, with the others turn the 
ring until one of the screw holes is brought into view; in this 
thrust a stout splinter of wood or a small wire, so as to hold the 
ring while the other screws are withdrawn ; the ring is then taken 
out and is ready for the wires. 

For these the web of the spider is to be preferred above any 
thing else, but when this is not obtainable a fine silk fibre may be 
substituted. 

We usually procure our webs from the living manufacturer 
directly, selecting those of a yellowish-brown color as furnishing 
the most perfect. product. 

The spider being held between the thumb and fingers of an as- 
sistant in such a posifion as to suffer no serious injury, and at the 
same time be unable to make any effectual resistance with his ex- 
tremities, the little fibre may be drawn out at pleasure, and being 
placed in the fine limes cut on the surface of the diaphragm, is 
then firmly cemented to its place by applying softened beeswax 
with the point of a knife blade. 


36 THE VERNIER TRANSIT. 


In case the spider is not procurable, a fine strand of a web- 
which is free from dust and long enough to serve for both wires, 
may be selected. 

In such times as the spiders remain in their winter quarters, we 
have been able to procure very good fibres froma box in which 
a number had bgen confined. ‘ 

When the wires are cemented, the ring is returned to its posi- 
tion in the tube, and either pair of screws being inserted, the 
splinter or wire is removed and the ring turned until the other 
screws can be replaced. 

Care must also be taken that the same side of the ring is 
turned to the eye-piece as before it was removed. 

When this has been done, the eye tube is inserted and its center- 
ing ring brought into such a position that the screws im it can be 
replaced, and then by screwing on the end of the telescope, the 
little cover into which the eye tube is screwed, the operation will 
be completed. 

To CLeaAn tHe TreLescopr.—The only glasses that will ordi- 
narily require cleaning are the object glass on its outside surface, 
and the little eye lens, which is exposed when the cap of the eye 
tube is removed. 

To remove the dust from these use a very soft and clean silk or 
cotton cloth, and be careful not to rubythe same part of the cloth 
a second time on the surface of the glass. 

No one should ever be allowed to touch the glasses with the 
fingers or with a dusty cloth. 

Excellencies of the Vernier Transit. 

These are due chiefly to the telescope and its attachments, and 
from what has been already said, it will appear are such as to ren- 
der this instrument greatly superior to one provided with the or- 
dinary sights. 

1. The magnifying power of the telescope enables the surveyor 
to take accurate observations at distances entirely beyond the 


reach of the naked eye. 


NEEDLE INSTRUMENTS. id 


2. The fine intersection of the cross wires can be set precisely 
upon the centre of the object. 

3. The revolving property of the telescope gives the means of 
running long lines up or down steep ascents or descents with per- 
fect ease, where, with the short sights of the ordinary compass, 
two or three observations would have to be taken. 

4, The use of a telescope entirely avoids the incessant trying 
of the eyes, experienced in surveys with the ordinary sights. 

5. With the telescope, lines can be run through the forest or 
brushwood, and the flagstaff distinguished with much greater cer- 
tainty than with the sights of a compass. 

This statement may appear very unreasonable to those not fami- 
liar with the instrument, and these in fact, raise the greatest ob- 
jection toa telescope, from its supposed unfitness for surveys in 
such locations. 

They have only to use it a few times in this kind of work, in 
connection with a flagstaff, painted white or covered with paper, 
to distinguish it from the surrounding objects, to be convinced of 
its great superiority. 

In the Vernier Transit, as furnished by us, is supplied, as we 
believe to the surveyor, the most perfect of all needle intruments, 
and this at a cost but little above that charged by other makers 
for a sight compass. 

The advantages of the telescope and its attachments are so 
great, that a surveyor, accustomed to them, would find it difficult 
to content himself with the ordinary compass, and such in fact is 
the universal testimony of those familiar with the Vernier Transit. 


GENERAL REMARKS. 


We have now described the instruments included under the 
division termed Needle Instruments, in the beginning of this 


work. 
4 


38 NEEDLE INSTRUMENTS. 


As there stated, the Plain and Vernier Compasses and the Ver- 
nier Transit depend for their accuracy and value, mainly upon 
the perfection of movement, of the magnetic needle. 

With such instruments, the greater part of the surveymg in 
our country has been, and will for a long time in the future, con- 
tinue to be done. 

With the improvements made in these instruments, a good sur- 
veyor may, with great care and skill, do work with a surpris- 
ing degree of accuracy and perfection, and yet all needles are 
liable to many irregularities. 

Imperfections of the Needle. 

These may arise either from the loss of magnetic virtue in the 
poles, the blunting of the centre pin, or the attraction exerted 
upon it by bodies of iron whose presence may be entirely unsus- 
pected. : 

The two first of these errors may be easily remedied in the 
manner we have described. 

Locan Arrraction.—This third and most frequent source of 
inaccuracy, may be detected by taking back sights as well as fore 
sights upon every line run with the needle, and by the agreement 
of the bearings the true direction of the line is determined. 

Sometimes a compass may have little particles of iron concealed 
within the surface of the metal circle or plates. 

It is the business of the maker to examine every instrument, 
in search of this defect, by trying the reversion of the needle 
upon all points of the divided circle. 

If the needle should fail to reverse when the compass is turned 
half around and the sights directed a second time upon any object, 
the instrument should be thrown aside and never sold. 

Besides the difficulties caused by the above imperfections, the 
variation of the needle is a frequent source of annoyance. 

What is termed the secular variation, we have already men- 
tioned in our account of the Vernier Compass, we will now speak 
of the 


NEEDLE INSTRUMENTS. 89 


Drurnat Varration.—This is caused by the influence of the 
sun, which in summer will cause the needle to vary from ten to 
fifteen minutes in a few hours, when exposed to its fullest 
influence. 


To guard against these causes of inaccuracy in the use of 


‘needle instruments, the surveyor will need the greatest care and 


attention; and yet, with all the precautions that can be suggested, 
the difficulty of measuring horizontal angles with certainty and 
to a sufficient degree of minuteness by the needle alone, has caused 
a demand to be felt more and more sensibly in all parts of the 
country for instruments, in the use of which, the surveyor may 
proceed with assured accuracy and precision. 

Indeed, in Canada, so great is the distrust of needle instru- 
ments, that the Provincial Land Surveyors are forbidden to use 
an instrument in their land surveys, unless it is capable of taking 
angles independently of the needle. 

To supply the demand thus created for increased perfection in 
the implements of the surveyor, we manufacture a variety of in- 
struments: two of which we shall now describe, under the names 


of The Railroad Compass, and The Surveyors’ Transit, 


SURVEYING INSTRUMENTS. 


THE RAIL ROAD COMPASS. 
Fig. 10. 


As shown in Fig. 10, this instrament has the main plate, levels, 
sights, and needle of the ordinary instrument, but is also provided 
with a circle on the outside of the compass box, divided all around 
and reading by two opposite verniers to single minutes of a 
degree. 


The opening through which the divided circle and verniers are 


seen, are closed by plates of glass, so as to effectually exclude the 


dust and moisture; the openings are now made on the sides, at~ 


right. angles to the position they oceupy in the cut, in order to 
read the divisions with greater convenience, 


THE RAIL ROAD COMPASS. Al 


The verniers are fixed to the main plate, and this, by a contri- 
vance of our own invention, has long sockets which give it great 
stability, and a motion around the circle almost perfectly free from 
friction. 

In this arrangement, the compass circle is very firmly attached 
to the socket, of which the lower part only is seen in the cut. 

The yvernier or main plate moves around the divided circle or 
limb, the divisions on both vernier and limb being horizontal and 
in the same plane. 

There is also, béneath the main plate, a clamp and tangent 
movement, by which, after the main plate has been moved nearly 
in position by the hand, it can be clamped to the socket, then 
with the tangent screw, the verniers, are moved slowly around 
the limb, and the sights fixed upon the desired object with the 
greatest precision. 

The graduated circle or limb is divided to half degrees, and 
figured in two rows, viz: from 0° to 90°, and from 0° to 360° ; 
sometimes but a single series is used, and then the figures run 
from 0° to 360°, or from 0° to 180° on each side. 

The figuring, which is the same upon this as in the other angu- 
lar instruments we shall hereafter describe, is varied according to 
the taste of the engineer, the first method is our usual practice. 

Tut VeERNtERS are double, having on each side of the zero 
mark thirty equal divisions, corresponding precisely with twenty- 
nine half degrees on the limb. 

They thus read to single minutes, and the number passed over 
is counted from the zero mark in the same direction in which the 
vernier is moved. 

The use of two opposite verniers in this and other mstruments 
gives the means of “ cross questioning” the graduations, the per- 
fection with which they are centered, and the dependence which 
ean be placed on the accuracy of the angles indicated. 

The movement of the vernier plate with the sights attached 
around the compass circle, gives the surveyor the power of laying 

4% 


7 


49, THE RAIL ROAD COMPASS. 


off the variation of the needle, while the graduated circle enables 
him to take horizontal angles with great accuracy, and minute- 
ness entirely independent of the needle. 


Tur Nerepte of this instrument is about five and a half inches 
long, and made precisely like those previously described. 


Tur Apsustments of this instrument, with which the surveyor 
will have to do, have been already described. 


To use the Rail Road Compass. 


It can be set upon the common compass ball, or still better, the 
tangent ball already described, placed either in a jacob-staff socket, 
or, as most surveyors prefer, in a compass tripod. 


We have also adapted to many of these instruments, the level- 
ing tripod head, with clamp and tangent movement described on 
page 46, and this is preferable to any other support. 

To take Horizonran AneLES.—First level the plate, and set 
the limb at zero, fix the sights upon one of the objects selected, 
and clamping the whole instrument firmly to the spindle, un- 
clamp the vernier plate and turn it with the hand, until the sights 
are brought nearly upon the second object; then clamp to the 
limb, and with the tangent screw fix them precisely upon if. 


The number of degrees and minutes read off by the vernier, 
will give the angle between the two objects taken from the centre 
of the instrument. 


It will be understood that the horizontal angles can be taken in 
any position of the verniers, with reference to the zero point of 
the limb; we have given that above as being the usual method 
and liable to the fewest errors. 


It is advisable where great accuracy is required, in this and 
other instruments furnished with two verniers, to obtain the read- 
ings of the limb from both, add the two together and halve their 
sum; the result will be the mean of the two readings, and the 
true angle between the points observed. 


THE RAIL ROAD COMPASS. 43 


Such a course is especially necessary when the readings of the 
verniers essentially disagree, as may sometimes happen when the 
instrument has been injured by an accident. 

TO TURN OFF THE VARIATION OF THE NEEDLE.—Having leveled 
the instrument, set the limb at zero, and place the sights upon the 
old line, note the reading of the needle, and make it agree with 
that given in the field notes of the former survey, by turning the 
whole instrument upon its spindle. 


Now clamp to the spindle, unclamp the vernier plate and again 
fix the sights upon the old lme; the number of degrees or minutes 
passed over by the vernier, will be the change of variation in the 
interval between the two surveys. 

To Survey with this instrument, the opeeator should fix the 
south side of the compass face, towards that end of the main plate 
which has the spirit level placed cross wise, and having brought 
the zeros of the limb, and vernier plate in contact, clamp them, 
and proceed as directed in our aecount of the Vernier Compass. 

Of course, it will be understood that lines can be run and angles 
measured, by the divided limb and verniers, entirely independent 
of the needle, which in localities where local attraction is mani- 
fested is very serviceable. 

The accuracy and minuteness of the horizontal angles, indicated 
by this instrument, together with its perfect adaption to all the 
purposes to which the Vernier Compass can be applied, have 
brought it into use in many localities, where the land is so valuable 
as to require more careful surveys than are practicable with a 
needle instrument. 


SURVEYING INSTRUMENTS. . 


THE SURVEYOR’ TRANSIT. 
Figs “V1. 


The Surveyors’ Transit, of which the above cut is a represen-. 
tation, is in principle, very similar to the instrument just described, 
Ronde from it mainly in the substitution of the telescope with 
its appendages, for the ordinary compass sights. 


THE SURVEYORS’ TRANSIT. 45 


Tue TELEscorr is of somewhat finer quality than that used 
with the Vernier Transit; as here shown, it is furnished with a 
small level, having a ground bubble tube and a scale ; sometimes 
also a vertical circle is connected with its axis, 


Ture STanparps are made precisely like those of the Vernier 
Transit, the bearings of the axis of the telescope being conical 
and fitted with the utmost nicety ; there is also m one of them 
the movable piece for the adjustment of the wires to the tracing of 
a vertical line. 

Tur Spirit Levets are placed above the upper surface of the 
vernier plate, one being fixed on the standard so as not to obstruct 
the light which falls on the vernier opening beneath. 

Both levels are adjustable with the ordimary steel pin. 

Tur Neep ir, like that of the previous instrument, is five and 
a half inches long. 

THe Vernier Prats, which carries the verniers and telescope, 
is made to move with perfect ease and stability around the gradu- 
ated circle or limb, attached to the compass box, thus allowing the 
telescope and verniers to be set to any variation of the needle, 
and turn off horizontal angles m any direction. 

Tue VeERNIERS, as in all our angular instruments, are double 
reading either way from the centre mark, and to single minutes 
of a degree. 

There are two verniers placed on opposite sides of the imstru- 
ment at right angles to the telescope; only one of these is shown 
in the cut. 

Tur Divipep Circte or limb is graduated to half debrees, 
reads to minutes by the verniers, and is figured as described in 
our account of the previous instrument. 

Tur Cramp anp TanceNT movement of the vernier plate is 
the same as that of the Rail Road Compass; it is partly shown in 
the figure. 

Tue Trirop Hrav.—tThis instrument should always be used 
on a leveling tripod. 


46 THE SURVEYORS’ TRANSIT. 


The one shown in the cut, and which is termed the Light Level- 
ing Tripod, has the upper parallel plate thickened on its under 
side, so as to give a long bearing for the four leveling screws. 

, The under plate supports the feet of the screws, and has beneath 
a cavity or bowl, in which moves a hemispherical nut screwed to 
the spindle of the tripod. 

This nut serves both to connect the plates together, and as a 
support on which the upper plate is moved by the- leveling 
SCreWS. 

The under parallel plate has also a screw on the under side, by 
which the tripod head may be disconnected from the legs, and 
packed in a box with the instrument. 

The leveling screws are made of bell metal, have a large double 
milled head and a deep screw of about forty threads to the inch ; 
their ends set into little brass cups, so that the screws are worked 
without indenting the under plate. Sometimes a piece of leather. 
is put in place of the cups. 

When the screws are loosened, the upper plate can be shifted 
around, so as to bring the leveling screws in any position with 
reference to the plates and telescope of the instrument. 

The clamp and tangent screws are seen on the upper plate of 
the tripod. 


The spindle of this tripod head rises above the upper plate, 
and the instrument can be removed from it, by pulling out a little 
pin made to spring into a groove, and thus keep the instrument — 
from falling when the tripod is carried upon the shoulder. 

In the lower end of the spindle and underneath the plates, is 
screwed the loop for attaching the string of the plumb-bob. 


In the operation of leveling the tripod, the engineer takes 
hold of the opposite screw heads with the thumb and fore finger 
of each hand, and turning both thumbs in or out, as may be 
necessary, raises one side of the upper parallel plate and depresses 
the other until the desired correction is made. 


THE SURVEYORS’ TRANSIT. 47 


To Adjust the Surveyors’ Transit. 

Tue LEVELS are adjusted with a steel pin as those of the Ver- 
nier Transit, and it need only be added here, that in this as well 
as Oiher instuments having two plates moving upon sockets inde- 
pendent of each other, the levels, when adjusted on one plate, 
should still keep their position when both are clamped together 
and turned upon a common socket. 

Otherwise, however accurately the telescope might trace a ver- 
tical line, when revolved upon the socket of one plate, it would 
give a very different result as soon as the position of the other 
plate was changed. 

THe NEEDLE and telescope with its other attachments being ad- 
justed, as described in our account of the Vernier Transit, we 
shall here consider only that of the 

Levet on TrLescorr.—For the adjustment of this attachment 
we shall give two methods, the first bemg that usually prac- 
tised by us: 

1. First level the instrument carefully, and with the clamp and 
tangent movement to the axis, make the telescope horizontal as 
near as may be with the eye, then having the line of collimation 
previously adjusted, find or place some good object. at a conve- 
nient distance, say from one to three hundred feet, which the hori¥ 
zontal wire will bisect; then, without moving the telescope, 
tarn the instrument upon the spindle, and with the same wire find 
or place another object in the opposite direction, and at the same 
distance from the instrument as the first point selected. 

These two points will be in the same horizontal line, however 
much the telescope may be out of level. 

Having determined these, and still retaining them, remove the 
instrument one or two hundred feet to one side of either of these 
points, level it again and bring the wires upon the nearest object. 
Then turn the instrument in the direction of the other, and note 
the position of the horizontal wire. 

If it does not bisect the point, the telescope is not horizontal, 
and the wire must be carried back over half the error, by moving 


48 THE SURVEYORS’ TRANSIT. 


the telescope with the tangent screw. When this has been done, 
the engineer needs only to alter the position of the level, by the little 
nuts at the ends, until the bubble is brought into the centre of the 
tube, when, if the telescope has not been moved from the point 
where it was fixed, the adjustment will be completed. 

2. Choose a piece of ground nearly level, and having set the 
instrument firmly, level the plates carefully, aud bring the bubble 
of the telescope into the centre with the tangent screw. Measure 
in any direction from the instrument, from one to three hundred ~ 
feet, and drive a stake, und on the stake set a staff and note the 
height cut by the horizontal wire, then take the same distance’ 
from the instrument in an opposite direction and drive another 
stake. 


On that stake set the staff and note the height cut by the wire 
when the telescope is turned in that direction. 

The difference of the two observations is evidently the differ. 
ence of level of the two stakes. 


Set the instrument over the lowest stake, or that upon which 
the greatest height was indicated, and bring the levels on the 
plates and telescope into adjustment as at first. 


Then, with the staff measure the perpendicular distance from . 
the top of the stake to the centre of the eye-piece; from that dis: 
tance subtract the difference of level between the two stakes, and 
mark the point on the staff thus found; place the staff on the 
other stake, and with the tangent screw bring the horizontal wire 
to the mark just found, and the line will be level. 


The telescope now being level, bring the bubble of the level 
into the centre, by turning the little nuts at the ends of the tube, 
and noting again if the wires cut the point on the staff; screw up © 
the nuts firmly and the adjustment will be completed. 


With such a level carefully adjusted, the engineer by taking 
equal fore and back sights, can run horizontal lines with great 
rapidity, anda good degree of accuracy. 


* 


THE SURVEYORS’ TRANSIT. 49 


To use the Surveyors’ Transit. 


In surveying with this instrument, the plates must be set so 
that the zeros of the circle and the verniers correspond, and firmly 
clamped together, the south end of the compass face being turned 
towards the eye end of the telescope when it is in the position 
shown in Fig. 11. 

The surveyor may then proceed precisely as with the plain 
compass, ; 

To TurN orr AnNGLES.— When angles are to be measured inde- 
pendently of the needle, proceed precisely as directed in the 
description of the Rail Road Compass. 

The variation of the needle is also set off as mentioned in our 
account of that instrument. 

; Sizes of the Surveyors’ Transit. 

We mike two sizes of the Surveyors’ Transit; the largest re- 
presented in the cut, having a needle five and a half inches long, 
a limb of seven inches diameter, and weighing from twelve to 
thirteen pounds, with the tripod head attached. 

The smaller instrument, has a four inch needle, a limb of six 
inches, and is about one-fourth lighter. 

The larger size is more generally preferred, on account of the 
greater length of the needle, which renders it more sensitive, and 
better adapted to the purpose of the surveyor. 

Merits of the Surveyors’ Transit. 


In this instrument, as just described, the surveyor will recog- 
nize advantages not possessed by any other instrument with which 
we are acquainted. 

Having a long needle, it is excellent merely as a needle instru- 
ment, and combining also all the advantages of a telescope with 
the accuracy of a divided limb and verniers, and having also the 
means for turning off the variation of the needle, it is for a 
mixed practice of accurate surveying and engineering, such indeed 
as is required of most city engineers, the best instrument ever 


constructed. 
5 


50 THE SURVEYORS’ TRANSIT. 


The arrangement of the sockets which we have alluded to in our 
account of the Rail Road Compass, is very perfect and stable, and 
the movement of the plates almost entirely free from friction. 

We made the first of our Surveyors’ Transits about three years 
ago, and, from that time to this, have found their sale continually 
increasing, and those that have been in use satisfying imvariably 
the best expectations of the purchaser. 

The peculiar construction of the sockets and plates of this in- 
strument are entirely our own invention, and we feel the utmost 
confidence in recommending it to all whose practice is such as to 
require the use of the needle combined with that of the divided 
circle and yerniers. 


ENGINEERS’ INSTRUMENTS. 


THE ENGINEERS’ TRANSIT. 
Fig. 12. 


Having now described the various instruments employed in sur- 
veying, we shall consider those whose use belongs more especially 
to the practice of the civil engineer, and of these the first in im. 


portance is that termed the Engineers’ Transit. 


D2 THE ENGINEERS’ TRANSIT. 


It differs from the instrument just described in having the com- 
pass circle, verniers and standards, attached to the same plate 
and moving together above the divided circle or limb, 

The cut, Fig. 12, shows the general arrangement of the parts, 
a detailed description of which we will now proceed to give. 


Tue TreLescore is from twelve to thirteen inches long, having 
an object glass of one and three-eighths of an inch aperture, an 
eye-piece of very high magnifying power, and is of the finest 
quality. 

Like all those of our own instruments, it is capable of reversion 
only at the object end, though we have often, when desired, made 
the other or even both ends to reverse. . 

The rack and pinion movement of the object glass is usually 
placed, as shown on the top of the telescope tube, though some- 
times on the side, as the engineer may prefer. 

Pryton ro Hye Guass.— We have often adapted to the eye- piece’ 
of this and our other Transits, a rack and pinion movement which is 
placed on the side of the tube and is very excellent in bringing 
the cross wires precisely into focus. 


* 


Tue SHapre.—<A_ short piece of thin tube called a shade, is 
always made to accompany this and the previous instrument, and 
is used to protect the object glass from the glare of the sun, or 
from moisture; it must be removed whenever the telescope is 
reversed. 

The interior construction of the telescope is similar to those 
already described. 

THE STANDARDS are made of well hammered brass, firm and 
strong. They have the sliding-piece for the adjustment of the 
cross wires to a vertical line as described on page 31 in our ac- 
count of the Vernier Transit. 


Tue Lrnp or divided circle is seven and a half inches in diame- 
ter, is graduated to half degrees, and read by two opponite: ver- - 
mers to single minutes. 


THE ENGINEERS’ TRANSIT. 53 


Tur Verniers are double, reading both ways from the centre, 
and are placed on the sides of the plate at right angles to the 
telescope. 


Tur Nrep_x is five incheg long and is raised by a milled screw 
head shown in the cut, placed above the plate. 


Tur CLAMP AND TANGENT Screws are also above, so as to be 
very accessible, and out of the reach of ordinary accidents. The 
clamping of the limb is effected in the interior, the aperture being 
covered with a washer to exclude the dust and moisture. 


Tur Levers, as shown in the cut, are above; they are both 
adjustable with the ordinary steel pin. 


The glass vials used in the levels of this and the Surveyors’ 
Transit, are ground on their upper interior surface, so that the 
bubble moves very evenly and with great sensitiveness, 


Tur Tripop Heap of this instrument is made considerably 
heavier than that of the Surveyors’ Transit. 

The upper plate is about five inches diameter, made thick and of 
well hammered brass; into this are screwed the long nuts or sock- 
ets for the leveling screws, and on the upper surface is seen the 
clamp, with the two butting tangent screws. 

With these, the movement is made very slowly, and much 
more firmly than is possible with a single tangent screw. 

The leveling screws are of bell metal, and have a broad three 
milled head; they rest on the lower plate, in the little cups spo- 
ken of in our account of the previous instrument. 

The lower plate is a little smaller than the upper, milled on the 
edge, and made to connect, by a screw, with the tripod legs. 

This tripod head is attached to the sockets of the limb and ver- 
nier plate, and is removed with them, when the instrument is 
packed in the box for transportation. 

The loop for the plumb-bob is connected by a screw to the spin- 
dle of the yernier plate, so that it is always suspended from the 
exact centre of the instrument. 

5x 


54 THE ENGINEERS’ TRANSIT. 


The Attachments of the Transit. 

In the cut is shown the vertical circle of four and a. half ranhan : 

diameter, which is read by a double vernier to minutes, and. also 
the clamp and tangent movement to the axis of the telescope. — 

These with the addition of a level on the telescope are often 

used with this instrument, though the majority of engineers prefer 

“plain” telescope or one entirely destitute of these appendages. 


Micrometer. = 

It is sometimes very convenient in the.use of both the Transit 
aud Leveling Instrument, to employ some simple method of ascer- 
taining the distances of objects without resorting to actual meas- 
urements. 

This is well effected by what is termed a ‘‘ Micrometer,” by the 
French called “Stadia,” placed in the plane of the cross wires in 
the interior of the telescope. : 

In those we have sometimes made,:two horizontal wires are 
fastened to the diaphragm, at such a distance apart that they will 
just include the tenth of a foot on a rod placed one hundred. feet 
distant. 

When nicely adjusted to this interval they will cover two-tenths 
at two hundred feet; three, at three hundred, and in the same pro- 
portion for any intermediate or greater distance. 

In this manner the engineer can estimate the distances of his — 
assistants with surprising accuracy and by a simple observation. 

. To Adjust the Transit. 

The adjustment of this amstrument and its attachments have 
been described in our account of those previously considered, 

To use the Engineers’ Transtt. ; 

But little need be added to what has been already given in the 
previous pages. 

Tur NErEpLe is of service principally as a rough check upon the 
readings of the verniers in the measurement of horizontal angles, 
any glaring mistake being detected, by noticing the angles indi- 
cated by both, in the different positions of the telescope, 


THE ENGINEERS’ TRANSIT. 5d 


It may also be used as in the compass, to give the direction in 
which the lines are run, but its employment is only subsidiary to 
the general purposes of the Transit. 


Sizes of the Transit, 


We make two different sizes of this instrument; the “heavy ” 
Transit which we have described weighing, without the tripod 
legs, from fourteen to fifteen pounds, and the 


Liaur Transit, precisely similar in style, but about one-fourth 
smaller and lighter in all its parts. 


It has a telescope of about ten inches long, a four inch needle, 
and a limb of nearly six and a-half inches diameter, 


Besides the simple form of the Engineers’ Transit, we also 
make important modifications, which may be desired by the engi- 
neer; a few of these we shall now enumerate. 


The Watch Telescope. 


A telescope is sometimes attached to a socket, moving in a hol- 
low cylinder which surrounds the lengthened socket of the limb, 
and is thus capable of moving around under the plates, and of a 
short vertical motion. 


The cylinder which supports it, may be clamped firmly to the 
limb, and the wires of the telescope thus fixed upon any object, by 
the tangent moyement of the tripod head. 


The object of the watch telescope, is to guard against, and de- 
tect any inaccuracy arising from the disturbance of the limb, dur- 
ing the progress of an observation, or the measurement of angles. 


Thus, if the wires of both telescopes are fixed upon the same 
object, and the watch telescope kept still upon it, while the ver- 
nier plate is unclamped, and the upper telescope shifted. to the 
second -point, a reference to the watch telescope, will immediately 
betray any disturbance in the position of the limb. - 


But, in spite of its excellencies in cases where great nicety is 
required, the additional weight and complication of the watch 


~ 


56 THE ENGINEERS’ TRANSIT, 


telescope, have caused it to be regarded by most American engi- 
neers as an encumbrance, rather than an “advantage to the 
Transit. 

The Theodolite Axis. 

In place of the ordinary axis of the telescope represented in our 
engraving, we sometimes make one resembling the Y axis of the 
English Theodolite. 

This modification is desirable, in cases where this instrument is 
intended to subserve the purposes of both level and transit. 

In such an arrangement, the telescope is confined in the axis 
with clips, by loosening which, it may be revolved in the wyes, 
or taken out and reversed end for end, precisely like that of the 
leveling instrument. 

The standards also allow its transit, or complete revolution in 
a vertical direction. 

In such an instrument, the adjustment of the wires, and level 
of the telescope, is effected in the same manner as those of the 
leveling instrument, the tangent movement of the axis serving, 
instead of the leveling screws, to bring the bubble and wires into 
position. 

With this modification of the transit, we have also frequently 
added, that of a small level bar, wyes, Xc., into’ which the tele- 
scope may be transferred, making thus a minature leveling 
instrument. 

This may be placed upon the socket and tripod head of the 
transit, and made capable of taking levels with a good degree of 
accuracy. 

When desirable, a vertical wheel may be placed on the axis of 
the telescope of this instrument, and thus all the properties of the 
English Theodolite, united with those of the American Transit. 

Two Telescope Instruments. 

We have occasionally manufactured instruments provided with 
two telescopes, haying their centres in the same vertical line, and 
one above the other. 


THE ENGINEERS’ TRANSIT. 57 


The upper telescope has a range of about 35° each way, in a 
vertical direction, and like that of the Engineers’ Transit, is car- 
ried on a vernier plate, furnished with levels, needle and tangent 
movement, and reading to minutes on the horizontal limb; the 
lower one is placed in the centre of the expanded vertical axis of 
the limb, by which it is moved horizontally ; and it has also a 
range of about 20° each way in a vertical direction. 

When the line of eollimation of both telescopes, is fixed upon 
the same object, the zeros of the vernier and limb are in coinci- 
dence, and when the vernier plate is turned 180 degrees the 
wires of the telescopes will cut the extremities of a straight line, 
in one point of which, the centre of the instrument is placed. 

In the same manner, it is manifest that any angle may be laid 
off on the limb, and the points be indicated by the wires of both 
telescopes, without changing the position of the limb. 

The lower telescope may also be used as a guard or watch, to 
detect any disturbance in the instrument during the time of an 
observation. 


Terapia TTT 


"SL ‘Sly 
“AdOOSHTAL HONI ALNUML 


"IGAGT A AHL 


THE LEVELING INSTRUMENT. 


Of the different varieties of the Leveling instrument, that 
termed the Y Level, has been almost universally preferred by 
American engineers, on account of the facility of its adjustment, 
and superior accuracy. 

Of these Levels we manufacture four different sizes, having 
telescopes of sixteen, eighteen, twenty, and twenty-two inches 
long, respectively. 

The cut on the opposite page represents our twenty inch Level; 
that of the sixteen inch telescope will be shown beyond. 

We shall consider the several parts of the instrument in 
detail : 

THe TxLescore has at each end a ring of bell-metal, turned 
very truly and both of exactly the same diameter; by these it 
revolves in the wyes or can be at pleasure clamped in any position 
when the clips of the wyes are brought down Coen the rings, by 
pushing in the tapering pins. 

The telescope has a rack and pinion movement to both object 
and eye glasses, an adjustment for centering the eye-piece, shown 
at A A, in the longitudinal section of the telescope. (page 60,) 
and another seen at C C, for ensuring the accurate projection of 
the object-glass, in a straight line. 

Both of these are completely concealed from observation and 
disturbance, by a thin ring which slides over them. 

The telescope has also a shade over the object-glass, so made, 
that whilst it may be readily moved on its slide over the glass, it 
cannot be dropped off and lost. 

The shade of our sixteen inch level, is made to take off, hke 
that of the Engineers Transit. 


60 THE LEVELING INSTRUMENT. 


The interior construction of the telescope, 
will be readily understood from Fig, 14, 
which represents a longitudinal section, 
and exhibits the adjustment which ensures 
the accurate projection of the object-glass 
slide. 

As this is peculiar to our instruments, 
and is always made by the maker so per- 
manently as to need no further attention 
at the hands of the engineer, we shall here 
describe the means by which it is effected 
somewhat in detail. 

The necessity for such an adjustment 
will appear, when we state, that it is almost 
impossible to make a telescope tube so that 
it shall be perfectly straight on its: interior 
surface. 

Such being the case, it is evident that 
the object-glass slide which is fitted to this 
surface, and moves in it, must partake of 
its irregularity, so that the glass and the 
line of collimation depending upon it, though 
adjusted in one position of the slide, will be 
thrown out when the slide is moved to a 
different point. 

To prove this, let any level be selected 
which is constructed in the usual manner, 
and the line of collimation adjusted upon an 
object taken as near as the range of the 
slide will allow, then let’another be selected 
ag distant as may be clearly seen; upon 
this revolve the wires, and they will almost 
invariably be found, out of adjustment, 
sometimes to an amount fatal to any confi- 


THE LEVELING INSTRUMENT. 61 


dence in the accuracy of the instrument. The arrangement adopt- 
ed by us to correct this imperfection, and which so perfectly 
accomplishes its purpose, is shown in the adjoining cut, Wig. 14. 

Here are seen the two bearmgs of the object-glass slide, one 
being in the narrow bell metal rmg which slightly contracts the 
diameter of the main tube, the other in the small adjustable ring, 
also of bell metal, shown at C C, and suspended by four screws in 
the middle of the telescope. 

Advantage is here taken of the fact, that the rays of light are 
converged by the object-glass, so that none are obstructed by the 
contraction of the slide, except those which diverge, and which 
ought always to be intercepted, and absorbed in the blackened 
surface of the interior of the slide. 

Now, in such a telescope, the perfection of movement of the 
slide, depends entirely upon its exterior surfaces, at the points of 
the two bearings. - 

These surfaces are easily and accurately turned concentric, and 
parallel with each other and being fitted to the rings, it only re- 
mains necessary to adjust the position of the smaller ring, so that 
its centre will coincide with that of the optical axis of the object 
glass. 

When this has been once well done, no further correction will 
be necessary, unless the telescope should be seriously imjured. 

The manner in which the adjustment of the object glass slide is" 
effected will be considered when we come to speak of the other 
adjustments 

Rack AnD Pinron.—As seen in Fig. 13, our Level telescopes 
are usually furnished with the ordinary rack and pinion movement* 
to both object and eye tubes. 

The advantages of an eye-piece pinion, are, that the eye-piece 
ean be shifted without danger of disturbing the telescope, and that 
the wires are more certainly brought into distinct view, so as to 
avoid effectually any error of observation, arising from. what is 


termed the instrumental parallax. 
6 


~ 


62 THE LEVELING INSTRUMENT. 


The position of the pinion on the tube is varied in different in- 
struments according to the choice of the engineer. 

We usually place our object slide pinion on the top of Transit 
telescopes, and on the side of those of the Level. The pinion of 
the eye tube, is always placed on the side of the telescope. 


Tur Lever or ground bubble tube is attached to the under side 
of the telescope, and furnished at the different ends with the usual 
movements, in both horizontal and vertical directions. 

The aperture of the tube, through which the glass tube appears, 
is about five and one fourth inches long, being crossed at the cen- 
tre by a small rib or bridge, which greatly strengthens the tube. 

The level scale which extends over the@vhole length, is gradu- 
ated into spaces a little coarser than tenths of an inch, and fig- 
ured at every fifth division, counting from zero at the centre of 
the bridge; the scale is set close to the glass. 

The bubble vial is made of thick glass tube, selected so as to 
have an even bore from end to end, and finely ground on its up-- 
per interior surface, that the run of the air bubble may be uni-_ 
form throughout its whole range. 

The sensitiveness of a ground level, is determined best by an 
instrument called a level tester, having at one end two Y’s to hold 
the tube, and at the other a micrometer wheel divided into hun- 

_dredths, and attached to the top of a fine threaded screw which 
raises the end of the tester very gradually. 

The number of divisions passed over on the perimeter of the 
wheel, in carrying the bubble over a tenth of the scale, is the in- 
dex of thé delicacy of the level. In the tester which we use, a 
movement of the wheel ten divisions, to one of the scale, indicates 
the degree of delicacy generally preferred for rail road engineering, 

For canal work practice, a more sensitive bubble is often de- 
sired, as for instance, one of seven or eight divisions of the wheel, 
to one of the scale. 

Tue Wyes of our levels are made large and strong, of the 


THE LEVELING INSTRUMENT. 63 


best bell metal, and each have two nuts, both being adjustable 
with the ordinary steel pin. 

The clips are brought down on the rings of the telescope tube 
by the Y pins, which are made tapering, so as to clamp the rings 
very firmly. 

Tue Levert Bar is made round, of well hammered brass, and 
shaped, so as to possess the greatest strength in the parts most 
subject to sudden strains. 

Connected with the level bar is the head of the tripod socket. 

Tar Trreop Socket is compound; the interior spindle, upon 
which the whole instrument is supported, is made of steel, and 
nicely ground, so as to turn evenly and firmly in a hollow cylinder 
of bell metal; this again, has its exterior surface fitted and ground 
to the main socket of the tripod head. 

The bronze cylinder is held upon the spindle by a washer and 
screw, the head of this having a hole in its centre, through which 
the string of the plumb bob is passed. 

The upper part of the instrument, with the socket, may thus be 
detached from the tripod head; and this, also, as in the case of all 
our instruments, can be unscrewed from the legs, so that both 
may be conveniently packed in the box. 

A little under the upper parallel plate of the tripod head, and in 
the main socket, is a screw which can be moved into a correspond- 
ing crease, turned on the outside of the hollow cylinder, and thus 
made to hold the instrument in the tripod, when it is carried upon 
the shoulders, 

It will be seen from the cut, that the arrangement just described 
allows long sockets, and yet brings the whole instrument down as 
closely as possible to the tripod head, beth objects of great impor- 
tance in the construction of any instrument. 

Tue Tripop Heap has the same plates and leveling screws, 
as that described in the account of the Engineers’ Transit; the 
tangent screw, however, is commonly single. 

For our sixteen inch level we make a smaller tripod head, re- 
sembling that used with the lighter engineer’s transit. 


= ; aaa SNAG AGANRITAI GaGa 


‘CL ‘SLT 
“AAOOSHTHL HONI NHALXIS 


IGAH'T A HAL 


THE LEVELING INSTRUMENT. 65 


The Adjustments, 


Having now completed the description of the different parts of 
the Leveling Instrument, we are ready to proceed with their ad- 
justment, and shall begin with that of the object slide, which, 
although always made by the maker, so permanently as to need 
no further attention at the hands of the engineer, unless in 
cases of derangement by accident, is yet peculiar to our instru- 
ments and therefore not familiar to many engineers. 

To Apsust tHe Opsect Siipe.—The maker selects an object 
as distant as may be distinctly observed, and upon it adjusts the 
line of collimation, in the manner hereafter described, making the 
centre of the wires to revolve without passing either above or be- 
low the point or line assumed. 

Tn this position, the slide will be drawn in nearly as far as the 
telescope tube will allow. 

He then, with the pinion head moves out the slide until an ob- 
ject distant about ten or fifteen feet, is brought clearly in view ; 
again revolving the telescope in the Ys, he observes whether the 
wires will reverse upon this second object. 

Should this happen to be the case, he will assume, that as the 
line of collimation is in adjustment for these two distances, it will 
be so for all intermediate ones, since the bearings of the slide are 
supposed to be true, and their planes parallel with each other. 

If, however, as is most probable, either or both wires fail to re- 
verse upon the second point, he must then, by estimation, remove 
half the error by the screws C C, (Fig, 14,) at right angles to the 
hair sought to- be corrected, remembering at the same time, that on 
account of the inversion of the eye-piece, he must move the slide 
in the direction which apparently increases the error. When both 
wires have thus been treated in succession, the line of collimation 
is adjusted on the near object, and the telescope again brought upon 
the most distant point ; here the tube is again revolved, the rever- 
sion of the wires upon the object once more tested, and the cor- 


rection, if necessary, made in precisely the same manner, 
ae 


66 THE LEVELING INSTRUMENT. 


He proceeds thus, until the wires will reverse upon both objects 
in succession; the line of collimation will then be in adjustment 
at these, and all intermediate points, and by bringing the screw 
heads, in the course of the operation, to a firm bearing upon the 
washers beneath them, the adjustable ring will be fastened so as 
for many years to need no further adjustment. 

When this has been completed the thin brass ferule is slipped 


over the outside ring, concealing the screw heads, and avoiding 


o) 
the danger of their disturbance by an inexperienced operator. 

In effecting this adjustment it is always best, to bring the wires 
into the centre of the field of view, by moving the little screws 
A A, (Fig. 14,) working in the ring which embraces the eye- 
piece tube. 

Should the engineer desire to make this adjustment, it will be 
necessary to remove the bubble tube, in order that the small screw 
immediately above its scale may be operated upon with the 
screw-driver. 5 

The adjustment we have now given is preparatory to those 
which follow, and are common to all leveling mstruments of re- 
cent construction, and are all that the engineer will have to do 
with in using our own instruments. What is still necessary 
then is— 


1. To adjust the line of collimation, or in other words, to 
bring both wires into the optical axis, so that their point of 
intersection will remain on any given point, during an entire 
revolution of the telescope. 

2. Lo bring the level bubble parallel with the bearings of the Y 
rings, and with the longitudinal axis of the telescope. 

3. To adjust the wyes, or to bring the bubble into a position 
at right angles to the vertical axis of the instrument. 

To Apsust tHE Line or CoLimarion, set the tripod firmly, 
remove the Y pins from the clips, so as to allow the telescope to turn 
freely, clamp the instrument to the tripod head, and by the level- 


THE LEVELING INSTRUMENT. 67 


ing and tangent screws, bring either of the wires upon a clearly 
marked edge of some object, distant from one to five hundred 
feet. 


Then with the hand carefully turn the telescope half way around, 
so that the same wire is compared with the object assumed. 


Should it be found above or below, bring it half way back by 
moving the capstan head screws at right angles to it, remember- 
ing always the inverting property of the eye-piece; now bring 
the wire again upon the object and repeat the first operation until 
it will reverse correctly. 

Proceed in the same manner with the other wire until the ad- 
jusiment is completed. 

Should both wires be much out it will be well to brmg them 
nearly correct, before either is entirely adjusted. 

When this is effected, slip off the covering of the eye-piece cen- 
tering screws, shown in the sectional view, (Fig. 14,) at A A, 

c 


and move each pair in succession with a small screw driver, until 


the wires are brought into the centre of the field of view. 

The inversion of the eye-piece does not affect this operation, 
and the screws are moved direct. 

To test the correctness of the centering, revolve the telescope, 
and observe whether it appears to shift the position of an object, 

Should any movement be perceived, the centering is not per- 
fectly_effected. 

It may here be repeated, that in all telescopes the position and 
adjustment of the line of collimation depends upon that of the 
object glass; and therefore, that the movement of the eye-piece 
does not affect the adjustment of the wires in any respect. 

When the centering has been once effected it remains perma- 
nent, the cover being slipped over to conceal and protect it from 
derangement at the hands of the curious or inexperienced 


operator, 


68 THE LEVELING INSTRUMENT. 


To Apsust Ton Lever Buppir.—Clamp the instrument over 
either pair of leveling screws, and bring the bubble into the cen- 
tre of the tube. 


Now turn the telescope in the wyes, so as to bring the level 
tube on either side of the centre of the bar, Should the bubble 
run to the end it would show that the vertical plane, passing 
through the centre of the bubble, was not parallel to that drawn 
through the axis of the telescope rings. 

To rectify the error, bring it by estimation half way back, with 


the capstan head screws, which are set in either side of the level 


] 
holder, placed usually at the object end of the tube. 

Again, bring the level tube over the centre of the bar, and ad- 
just.the bubble in the centre, turn the level to either side, and, if 
necessary, repeat the correction until the bubble will keep its posi- 
tion when the tube is turned half an inch or more, to either side 
of the centre of the bar. 

The necessity for this operation arises from the fact, that when 
the telescope is reversed end for end in the wyes in the other and 
principal adjustment of the bubble, we are not certain of placing 
the level tube in the same vertical plane, and, therefore, it would 
be almost impossible to effect the adjusi'ment without a lateral 
correction. 


Having now, in great measure, removed the preparatory diffi- | 


culties, we proceed to make the level tube parallel with the 
bearings of the Y rings. 

To do this, bring the bubble into the centre with the leveling 
screws, and then without jarring the instrument, take the telescope 
out of the wyes and reverse it end for end. Should the bubble 
run to either end, lower that end, or what is equivalent, raise the 
other by turning the small adjusting nuts, on one end of the level, 
until by estimation half the correction is made; again, bring the 
bubble into the centre and repeat the whole operation, until the 
reversion can be made without causing any change in the bubble. 


THE LEVELING INSTRUMENT. 69 


It would be well to test the lateral adjustment, and make such 
correction as may be necessary in that, before the horizontal ad- 
justment is entirely completed. 

To Apsust tHE Wyrs.—Having effected the previous adjust- 
ments, it remains now to describe that of the wyes, or, more pre- 
cisely, that which brings the level into a position at right angles, 
to the vertical axis, so that the bubble will remain in the centre 
during an entire revolution of the instrument. 

To do this, bring the level tube directly over the centre of the 
bar, and clamp the telescope firmly in the wyes, placing it as before, 
over two of the leveling screws, unclamp the socket, level the 
bubble, and turn the instrument half way round, so that the level 
bar may occupy the same position with respect to the leveling 
screws beneath. 

Should the bubble run to either end, bring it half way back by 
the Y nuts on either end of the bar; now move the telescope 
over the other set of leveling screws, bring the bubble again into 
the centre and proceed precisely as above described, changing to 
each pair of. screws, successively, until the adjustment is very 
nearly perfected, when it may be completed over a single pair. 

The object of this approximate adjustment, is to bring the upper 
parallel plate of the tripod head into a position as nearly horizontal 
as possible, in order that no essential error may arise, in case the 
level, when reversed, is not brought precisely to its former situation. 
When the level has been thus completely adjusted, if the instrument 
is properly made, and the sockets well fitted to each other, and the 
tripod head, the bubble will reverse over each pair of scréws and 
In any position. 

Should the engineer be unable to make it perform correctly, he 
should examine the outside socket carefully to see that it sets se- 
curely in the main socket, and also notice that the clamp does not 
bear upon the ring which it ertcircles. 

When these are correct, and the error still is manifested, 1t will, 
probably, be in the imperfection of the interior spindle. 


70 THE LEVELING INSTRUMENT. 


After the adjustments of the level have been effected, and the 
bubble remains in the centre, in any position of the socket, the 
engineer should carefully turn the telescope in_the wyes, and sight- 
ing upon the end of the level, which has the horizontal adjustment 
along each side of the wye, make the tube as nearly vertical as 
possible. 

When this has been secured, he may observe, through the tele- 
scope, the vertical edge of a building, noticing if the vertical 
hair is parallel to it; if not, he should loosen two of the cross 
wire screws at right angles to each other, and with the hand 
on these, turn the ring inside, until the hair is made vertical; the 
line of collimation must then bescorrected again, and the adjust- 
ments of the level will be complete. 


To use the Level. a 


When using the instrument the legs must be set firmly into the 
ground, and neither the hands nor person of the operator be 
allowed to touch them, the bubble should then be brought over 
each pair of leveling screws successively, and leveled in each posit- 
tion, any corrections being made in the adjustments that may ap- 
pear necessary. 


Care should be taken to bring the wires precisely in focus, and 
the object distinctly in view, so that all errors of parallax may be 
avoided. 


This error is seen when the eye of an observer is moved to either 
side of the centre of the eye-piece of a telescope, in which the 
foci of the object and eye-glasses, are not brought precisely upon 
the cross wires and object ; in such a case, the wires will appear 
to move over the surface, and the observation will be liable to in- 
accuracy. ; 

Tn all instances the wires and object, should be brought into 
view so perfectly, that the spider lines will appear to be fas- 
tened to the surface, and will remain in that position however the 
eye is moved. 


THE LEVELING INSTRUMENT. ah 


If the socket of the instrument becomes so firmly set in the tri- 
pod head as to be difficult of removal in the ordinary way, the 
engineer should place the palms of his hands under the wye nuts 
at each end of the bar and give a sudden upward shock to the bar, 
taking care also to hold his hands so as to grasp it the moment it 
is free. 

, The Farm Level. 

Besides the various engineers levels, we make a smaller 
and Cheaper instrument, styled the Farm Level, for laying out 
mill seats, draining lands, and such other purposes as wall readily 
oceur to the intelligent agriculturist. 

This instrument has a telescope of from fourteen to sixteen 
inches long, with Y and bubble adjustments and leveling tripod, 
like one of the larger instruments. 

The tripod head is made like that figured in the cut of the 
Surveyors’ Transit, but is usually without the clamp and tangent 
movement. 

There is, however, a clamp screw on the side of the socket by 
which it may be held on the spindle, while the adjustments are 
being perfected. 

Builders’ Level. 

We have also made several small levels for Masons use, similar 
to that just described, but generally more perfect and expensive. 

These instruments have been found extremely serviceable in 
the construction of extensive buildings, on account of the facility 
with which level points may be determined on every side, by the 
simple revolution of the telescope. 


LEVELING RODS. 


The two kinds most generally used by American engineers, are 
both sliding rods, divided into hundredths of a foot and reading by 
verniers to thousandths. 


Boston Rod. 


That known as the Boston or Yankee Rod, is formed of two 
pieces of light baywood or mahogany, each about six and a half 
feet long, connected together by a tongue, and sliding easily by 
each other, in both directions. 

One side is furnished with a clamp screw and vernier at each 
end, the other carries the divisions, marked on strips of satin wood, 
inlaid on either side. : 

The target is a rectangle of wood, fastened near one end of the 
divided side, and having its horizontal line just three-tenths from 
the extremity. 

The target being fixed, when any height is taken above six 
feet, the rod is changed end for end, and the divisions read by the 
other vernier ; the height to which the rod can be extended, be- 
ing a little over eleven feet, 

This kind of rod is very convenient from its great lightness, but 
the parts are made too frail to endure the rough usage of this 
country, and, therefore, American engineers have generally given 
_the preference to another, made heavier and more substantial. 

The New York Rod. 

This rod, which is shown in the engraving, as cut in two, so 
that the ends may be exhibited, is made of satin wood, in two 
pieces like the former, but sliding one from the other, the same 
end being always held on the ground, and the graduations starting 
from that point. 


‘LEVELING RODs. 73 


The graduations are made to tenths and hun- 


dredths of a foot, the tenth figures being black, — 


and the feet marked with a large red figure. 

The front surface, on which the target moves, 
reads to six and a half feet; when a greater 
height is required, the horizontal line of the tar- 
get is fixed at that point, and the upper half of 
the rod, carrying the target, is moved out of the 
lower, the reading being now obtained by a 
vernier on the graduated side, up to an eleva- 
tion of twelve feet. 

The mountings of this rod are differently 
made by different manufacturers. We shall 
give those which we have adopted. 

The target is round, made of thick brass, hav- 
ing to strengthen it still more, a rib raised on 
the edge, which also protects the paint from 
being defaced. 

The target moves easily on the rod, being 
kept in any position by the friction of the two 
flat plates of brass which are pressed against 
two alternate sides, by small spiral springs, 
working in little thimbles attached to the band 
which surrounds the rod. 

There is also a clamp screw on the back, by 
which it may be securely fastened to any part 
of the rod. 

The face of the target is divided into quad- 
rants, by horizontal and vertical diameters, 


which are also the boundaries of the alternate 


colors with which it is painted. 

The colors usually preferred are white and 
red; sometimes white and black. 

The opening in the face of the target is a 


i 


"4. s 


74 LEVELING RODS. 


little more than a tenth of a foot long, so that in any position a 
tenth or a foot figure can be seen on the surface of the rod. 

The right edge of the opening is chamfered and divided into ten 
equal spaces, corresponding with nine hundredths on the rod; the 
divisions start from the horizontal line which separates the colors 
of the face. 

The vernier, like that on the other side of the rod, reads to 
thousandths of a foot. 

The clamp, which is screwed fast to the lower end of the upper 
sliding piece, has a moveable part which can be brought by the 
clamp screw firmly against the front surface of the lower half of 
the rod, and thus the two parts immovably fastened to each other, 
without marring the divided face of the rod. 


THE POCKET COMPASS. 


This little instrument shown with jacob staff socket in Fig. 17, 
though not used in extensive surveys hke the larger compasses - 
we have described, is found very convenient in making explora- 
tions, or in retracing the lines of government surveys, as in loca- 
ting land warrants, &c. 

The sights are made with a slote and a hair on opposite sides ; 
they also have joints near the base so as to fold over each other 
above the glass when the compass is packed in its case. 

The circle is graduated to degrees, aud figured from 0 to 90 
each way, as in the larger instruments. 

The needle is suspended upon a jeweled centre and is raised by 
the lifter shown in the cut. 

The jacob staff socket is often used with the compass, being 
screwed to the under side and detached at pleasure. 

The mountings are all that are furnished, the staff itself being 
easily made out of a common walking stick. 

We make two sizes of the pocket compass, differing mainly in 
the needle, which in one is two and a half, in the other three and 
a half inches long. 


GENERAL MATTERS. 


Tripods. 


In the tripods of all our instruments, the upper part of the leg 
is flattened, and fitted closely in the surfaces of the brass cheek 
pieces. 
The cheeks are made very broad, and give a firm hold upon the 
leg, which may be tightened at any time, by screwing up the 
bolts, which pass through the top of the legs; this is especially 
necessary after the surface of the wood has been much worn, 

The legs are round, and taper in each direction from a swell, 
turned about one-third the way down, from the head to the point. 

The point, or shoe, is a tapering brass ferule, havimg an iron 
end; it is cemented and riveted firmly to the wood. 

The legs of all our tripods are about four feet eight inches long 
from head to point. We make three sizes of tripods, which we 
will now separately describe. 

1. Tue Compass Trrpop, seen in part in the cut of the ver- 
nier transit, and having the brass plate, to which the cheeks are 
attached, three and three-fourth inches in diameter, and legs 
which are about one inch at the top, one and three-eights at the 
swell and seven-eights at the bottom. 

The legs are usually made of cherry, sometimes of mahogany, 
and the tripod is used with the various kinds of compasses and 
with the vernier transit. 

2. Ture Mrpium Sizmp Tripop, shown with the surveyors’ 
transit, and having a plate of same diameter as above, but with 
the cheeks made considerably broader, by curving at each end; 
the legs being also about an eighth of an inch larger throughout. 

This tripod has mahogany legs, and is used with the surveyors’ 
transit, the light engineers’ transit and the sixteen inch level. 


CHAINS. TT 


3. Tue Heavy Tripop, shown with the engineers transit, hav- 
ing a brass plate of four and one-fourth inches diameter, with ex- 
tended cheek pieces, and with legs one and three-eighths of an 
inch at the top, one and three-fourths at the swell, and one and 
an eighth at the point. 

The heavy size has also mahogany legs, and is used with the 
engineers transit, and larger leveling instruments. 

Lacquering. 

All instruments are covered with a thin varnish, made by dis- 
solving gum shellac in alcohol, and applied when the work is 
heated. 

As long as this varnish remains, the brass surface will be kept 
from tarnishing, and the engineer, by taking care not to rub his 
instrument with any dusty cloth, or to expose it to the friction of 
his clothes, can preserve its original freshness for a long time. 

Bronze Finish. 

Instead of the ordinary brass finish, some engineers prefer in- 
struments blackened or bronzed. This is done with an acid 
preparation after the work has been polished, and gives the instru- 
ment a very showy appearance, besides being thought advantageous 
on account of not reflecting the rays of the sun as much as the 
ordinary finish, 

When well lacquered, the bronzing will last a considerable 
time, but as soon as it becomes a little worn the appearance of the 
instrument is much worse than one finished in the usual style. 


CHAINS. 


pee eg ge 
Four Pole Chains. 

The ordinary surveyor’s chain igs sixty-six feet, or four poles 

long, composed of one hundred links, each connected to the other 

by two rings, and furnished with tally marks at the end of every 


ten links. 
7* 


78 CHAINS. 


We make our chains of the best No. 8 iron wire, the rings 
being sawed and the ends of the link filed and bent close, so as to 
avoid kinking. 

A link in measurement includes a ring at each end. 

The handles are of brass, each forming part of the end link, 
and connected to it by a nut, by moving which the length of the 
chain is adjusted, ; 

The tallies are also of brass, and have one, two, three, or four 
notches, as they are ten, twenty, thirty or forty links from either 
end; the fiftieth link is rounded, so as to distinguish it from the 
others. 

Two Pole Chains. 


A chain of .two rods, or thirty-three feet long, is often used by 
surveyors, and we have occasionally made our four pole chains so 
that by detaching a steel snap in the middle, the parts could be 
separated, and the handle being transferred to the forty-ninth lnk 
in the same mannez, a two pole chain is readily obtained. 

Eingineers’ Chains 

Differ from the common or Gunter’s chain in that the links are 
each one foot long; the wire is also much stronger. They are 
fifty or one hundred feet long, furnished with handles and tallies, 
and usually with a swivel in the middle, so as to avoid twisting. 

The wire of our Engineers’ chain is of size No. 5 or 6, and the 
whole is made in the most substantial manner. 

In the place of the round rings ordinarily used, we have lately 
substituted in these chains other rings of an oval form, and find 
them about one-third stronger, when made of the same kind of wire. 

Steel Chains. 

These are often preferred, on account of their greater lightness, 

and are made of any desired length; their cost is about double 


that of iron chains, 
The wire used in our steel chains is of size No. 10, and is very 


stiff and strong. 


TAPE MEASURES. 79 


Marking Pins. 

With the chain there are also needed ten marking pins or chain 
stakes, made of stout iron wire, about twelve inches long, pointed 
at one end to enter the ground, and formed into a ring at the 
other, for convenience in handling. * 

The length of a chain should always be taken from its extreme 
ends, so that the pins are set on the outside of the handles. 

It is best that the surveyor carefully lay down on the surface 
of the ground the length of his chain while it is yet new, and 
mark the points by monuments, the position of which will not be 
disturbed by the frost or accident. 

He will thus have a standard measure, to which his chain may 
be adjusted in case of alterations to which all are liable. 

IN USING THE CHAIN it should be drawn straight, and examined 
at intervals so as to detect and remove any kinks or other cause 
of inaccuracy. 


TAPE MEASURES. 


The best are Chesterman’s steel tapes, made of a thin ribbon of 
steel, which is jointed at intervals, and wound up in a leathern 
ease, having a folding handle. 

These tapes are of all lengths, from thirty-three to one hundred 
feet, divided into inches and links, or more usually, tenths of a 
foot, and links, the figures and graduations being raised on the 
surface of the steel. 

The great cost of the steel tape has always prevented its gen- 
eral use, and the metallic tape of the same manufacturer is the 
only one commonly employed in American Engineering, 

These are of linen, and have also fine brass wires interwoven 
through their whole length. 

They are thus measurably correct, even when wet. 

They are mounted like the steel tapes, of like lengths, and 
similarly graduated. 


TABLE OF CONTENTS. 


Drawing instruments—see “supplement.”...... 


eeeeoerreeeerere 


Electricity on compass glass,.........eeee ees . Rear ee 
Eye piece, how composed,...........+- saw eeres +o dulge Ree 
cs mes wenCentredh  eccee. ue ogi 0 wuctbe veuatete le tenant Agha 


Excellencies of the Vernier Transit, ........cccccccecccseccsce 


Farm level,..... etalon ta jorasenes oie 1S Wi oaewale eo rete 0 iSwet.es canteen 
Glass of Compass, how replaced,....... G Lines sib vod o's eR 133i eayiy 
General remarks,........ He pvecueieieie dis sell Boe geet aterate enevete 
Wy MIRAGE UG, ve torer siete oleleie a7otel ahs ie ons| 6 nisl Srtiok Gea a eeldlayelareeiate A 
SPEOUDCAGVGISN sis 4s a u.e% ie sb 5:0 fame" Sbld paw legates te Beto) 
Jacob-staff socket, ........... sales sidisl'siign 6 igretare ¢. alle o?ecallelanaeeetameae 
aeyels, ho wsTeplaced joe sii ee ts os lp apse Ws selene. eave ‘na uae : 
Leveling screws,....... woe sie ele aie. Gewelfes sine’ lace aleleteters Ano 
oh ANSEPUMIOHE C ssra sho-w:c euler e eleeis os ore ale ie Sites areeioree Saale 
cs LOGS, PB OSbOH, I afocars anckale tales ar aush ne eitsie.s clearer ° sonar 
is oh eee NOW LOL keene. 6 resis ste Pee tT ore 
Level tester,,..... aig ou plaid aliel’el Bows w diel: bie ach Stee sie, ove lahat enna F 
Line of no variation........ a ies, b:8) Sage 8s 00.018 Gabe a creer ten 3% 
ocalmatirackiong. ss ate tomes aes BPE ERS aes dw oe sce lalegeieneneeretete 
Lacquering,..... adiion ddiscoddd sees sose ddd AsAoitode +> - sioleterste 
Nid King puis, 25 Svie-c% se stasioreeate oly ale God ela 1 at shale aiaietaanteiataes Siac 
Masons) evel cvcecehicote sate ces eee 6 val Me eRe ieioe ses 
Miierom eer ls sia cers. oso ecertepetel paiers ao see io! bonis) ¢ 0 0 econ eens . 
GO 16 IWSOLEAG, .de-5 2's, d:0:shaie, s-or0/s, ors ahegerelert Deny Mhalseeata ey d sJeletaroiars 
4 fs how, remagnetized.. 2 isst0. <..6c.. eeicie om eneeaiee 
ee < Variation: of diurnal; s-s../ssia cere serele Rie eters Sate 
“ s i $$ speCTlAar, ..siyieuSceo obe eke Semele 
5 imperfections Off. ....6 6 ni. os vale sess cele 
Widedle: instrpmentere wil (0. ders eos o's 0 sore oleie recipe aici ia eeamaene 
Object glass, how composed,..........seeceeeoes < Aateare o's wake 
tf slide Bow. SO} UstOd, .~ «ie leia¢ olnie Carte niains on 5 Seles 
Parallax instrumental jccriysciese\sicls cleyereteretereaeieretre siete volre agile 


tf IO WHAV OLUOA se Liem o's c ieee tee eta nearest eavens Sate ae ee 


Paar. 


85 


11 
19 
31 
36 


71 


12 
37 
16 
53 


7 


12 
46 
59 
72 
72 
62 
16 


TABLE OF CONTENTS. 


MIO SEIBESY Soda dived dune sin e o\etssie'.s6 urs bee cle sect sys 3% 
PRADO COMPAS) 6s. os oes sa oie enna AG Sine rst iid SURES NOW Gon 


Repairs of Compass, how made,..........+++eeeees Srey sabes hoes - 
se SoVornier Lransit,... 5... 0. MOS Cet cine. elas neta ts 


Sights of Compass,............+- act Caster kro ee Ret ears ae 
BEE SABTR Dyic: re 5c. 070 60 6's 5 HO goeAb OGS So erercastoKere A tic PE 6 
Sa on telescope, . .. 6%... Srafelele's win iefd ocsltus Spires ew sinls oie 
IEEE OAVSIOB ye as ops moe 658 Sin op Se nce abe oie swt Essie 
Sensitiveness of a level bubble, degree of,.............e0e scene 
IERCERTOIESEODGI le cioieic s <2 ole ee vine 086 veins a s.r w\sic'e 0 e/3\es'inie Fe 
Spring, Catch,.......... SERIOR OS ARCO SC COLO DEO en bya ohitoger ar okets 


Tangent Scale on sights,............4. sipreteeycisseletctetst jal ere, cieisere : 
Telescope of transit, sectional view of,...... OF oes 9 © sielelsiale vine Ss 
pie level, S bic ae ers eh ae 


“ magnifying power of, how ascertained,............+- 
‘« optical principles of,.......- Rus cbdoweoenet aa oose: 


BRMMATUUVOPUIGT Soha <'s'5. coo ce ne nerscce ess nope ts Soles eat seaieke 
Some BULVEY OTS, .... 0s s sepa SEO REEDED CLL CO OSS SORE bar 
=) -engmeers),...'...2...+ ASD SO UTOD daa Sb RLOt Ie CASS 

Tripod head, light,............ be Be Hie Vetewneis Camera 
% BMMEMOR VY 5 oc cco .0 ss 0b oman, 20/6 teed ne Goldin eo 0a 48 sinere 
SUMING EHIOFONG.S1Z69 Of, 6. 5.00%. vce e cinedcciceescee cos ae 

Two telescope instrument,.......... pike: et nite, *) eee 8 SECS 

Theodolite axis,...... Ra siavoitreyeze eictereisiete 1s etal UR yore Street 

CINE sig s'ms oo < no 3 60's patesets AGO Oc > cae aiaseteteconal crete 

Tapes, measuring, steel and metallic,............ ee ck ONE ee 


Wertieal CIPCle:. ....0seces ae sire, scapes tier oVersicl esis ae ose eheveo yrs é 
Vernier of compass,...... Sele heens sigaidiacgi er aers eseeees wisleje'ee es 
7 a OG, ss how read,........ BARONE oot cis araane lelest ens 


NINE SREIIO DIG eriiate > ain oo anise sr5.ec ails ee oc 0 vice on o,0\0.cieinyo.es 
OUR erie: cas sos viess cect aos sais ocicc ve cs eet 


» 


i= 


SUPPLE MENT TO MANUAL, 


DRAWING INSTRUME NTS. 


To guide the surveyor aud engineer in the selection of Drawing 
Instruments, we here add a detailed description, with illustrations 
and prices of the separate pieces, and cases of the different kinds 
in general use. 

Those we shall first mention are of German and French manu- 
facture, are of good quality and finish, and such as the great ma- 
jority of purchasers select and use. . 

The Swiss instruments are of better quality and finish, and are 


held at much higher rates. 


The prices given with all the instruments described are the 


same as those of other importers. 


FRENCH AND GERMAN INSTRUMENTS. 


II DRAWING INSTRUMENTS. 


FIGURE. PRICE, 
1. Brass Dividers, brass joints, rivet-heads, 5 inch 12 cts.,6inch  $0,18 
Laer ae Bu steel joints, screw-heads, 5 inch 25 ets., 6 inch sou 
1. Fine Dividers, steel joints, turned cheeks, 4 inch 50 ets., 5 inch 

62 cts, 6 inch, - - - - - - - - s75 
2. Fine Dividers, steel joints, hair spring, 5 inch $1,00, 6 inch, 1,37 
Daas Re iY «superior, 5 inch $1,837, 6inch 1,75 
1. German Silver, steel joints, turned cheeks, superior, 5inch, - 15 
L, x SF sf & se 6ineh, - 87 
2 S as és hair spring, fine, 5 inch $1,50, Gineh 1,75 
9, x i 4 “superior, 5 inch $1,75, 6 inch ~ 2,00 
3. Three legged Dividers, brass, $2,62, Ger. Silver $2,75, to - 8,50 

Bisecting, - - - - - - - - - ,50 


4, Pocket Dividers, German Silver, - - E S = 2,00 
5. Proportional Compasses, brass, $1,50 to $3; full divided $7 to 8,50 
5. ae os German Silver, $7,25 to - - 9,00 
6. Pillar Compasses, brass $5,50 and $5,75, Ger. Silver $6,75 and 6,00 
7. Dividers, bfass, 3 inch, with pen and pencil point, med. quality, 1,25 ~ 
ly Ger. Silver, “ < & fine . 2,50 


8 9 
8. Dividers, brass, 5 inch, med. quality, with pen and pencil point, ,75 
6 inch, . - - - - - - 87 
8. ss « 5 inch, med. quality, with addition of length- 
ening bar, - - - - - - - - - 87 
8. Dividers, German Silver, 6 inch, fine quality, pen, pencil, bar _ 
and needle point, - - - - - - - 8,25 


9. Furniture for Beam Compasses, brass, $3; with adjusting screw, 3,75 
9. ae Seas German Silver, $4,25 to - 5,00 


+ 
»~ 4 


DRAWING INSTRUMENTS. III 


BOW PENS AND PENCILS, SPACING DIVIDERS AND 
DRAWING PENS. 


12 

FIGURE. PRICE. 
10. Bow Pens, brass, 50 cts. to - - - - - - $1,25 
dig 2S “with joint in each leg, German Silver, - - 2,25 
Bow Pencils, <“‘ oC ts 8 sé - - 2:25 
12. Bow Pens, with adjusting screw, brass $1,25; German Silver, — 1,50 
Le as * Ly & “and hinge to pen, brass, - 1,50 
German Silver, - - - - - - - - 2,00 
12. Bow Pens and adj. screw and pencil point, German Silver, 2,25 

12. Bow Pens with adjusting screw, German Silver, with pencil 
and needle point and extra pen point, - - - 3,50 
13. Bow Pencils, solid steel German Silver or Ivory handies, — - 1,75 
14. Spacing dividers, “ Ki a - 1,50 
15. Bow Pens, % $6 e g - 1S 
16, Drawing Pens, 25, 87 and - - - - - - 300 
17. as “ with hinge, - - - - - - ,50 
lie if Ses oats “« and protracting pin, 62 and - a) 
rh a € sf “extra fine, - - - - 1,25 
17. a «all German Silver for red ink, : - Bil 
18. us “double or Railroad Pens, $1,75 and - 2,50 


19. Roulettes, for dotting lines, 50, 62 and - : = 2 s75 


TV, 


DRAWING INSTRUMENTS. 


SQUARES, PROTRACTORS, &C 


FIGURE, 22, 23 


20, 


Brass Protractors, assorted sizes, 124 ets. to - - 
“f « with steel blade, 2 to 8 feet long, - 
German Silver Protractors, with horn centre and movable arm, 
divided to 4 degrees, $4 to - - 


> 
German Sipord -rotractors, whole circle, horn centre and mo- 
vable arm, divided to + devrees, $4,75 to - =i 
Horn Protractors, 4 inch 124 cts, 5 inch 25 ets, 6 inch - 
Tvory Protractors for Engineers, 6 inch $1,50, $2, $2,50 and 
es He > oy 2} inch wide, very superior, 
6 inches long, $3,50 and - - - - 
Tyory Protractors for Engineers, 12 inch extra wide and full, 
Ivory Seales, 6 inch usnal quality, - - 


. [very Seales, 12 inch, chain on edge only, 20x40, 30x50, 40x60 


$2.25 to - - - - - - 
Toon Seales, 12 inch, chain on edge only, 50x109, - 

¥ os 12 inch, for Architects, 2 2525, 2,50, -3,00sand «2 = 
Ivory Seales, 12 inch, 16 scales off edge, in tenths or twelfths, 


$3,50 and - - : - 
Boxwood Seales, 6 inch, usual quality, - - - 

ee Protracting Seales, 6 inch, - - - 

if Seales, 12 inch chain, 10 to 60 on edge. - - 

Hs  “ 42 inch, 16 scales off edge in tenths and twelfths, 

ne “12 inch Architects, graduated from $ to 8 inches, 

“ce ce 


3 sided chain, giving 6 scales all on edge, —- 
Boxwood Seales, 3 sided Architects, giving 12 scales all on 
edge, $2,50 to - 2 3 2 


PRICE. 


$1,50 
7,50 


6,50 


DRAWING INSTRUMENTS. Vv 

FIGURE. PRICE. 

- 23. Boxwood Gunter Seales 1 foot 87 and 75 cts, 2 feet - s15 
o Pocket Rules, 1 foot, 4 fold, 25 to 75 ets, Ivory do, 

62 ets. to - - - - - - 2,00 
Paper Scales 18 inches long, in sets of six, graduated from 4 

to 3 inches, per set - : : 3s : 1,25 


28 


© © 


24 25 26 

24. T Squares, wood, with arm, 18 to 30 inches long, - $0,75 
0 i sf sf «* and swivel head, - - 1425 
Bee sh $f ee a aD * and brass edges 

to arm, $1,75 to - - - - - 2,50 
25. Irregular Curves, various sizes, 25 to 87 and - 00 
26. Ebony Triangles, 87 cts, Pear wood do. 3 - 20 
27, German Silver Squares and Triangles, 50 cts, to - 2,50 
28. Pins to fasten paper to the drawing board, brass, 25, 87 and 

50 cts. German Silver, per dozen, - - . ,60 


29. Horn Centres, to prevent the dividers from marking the paper, ,18 


VI “DRAWING INSTRUMENTS. 
FIGURE. PRIOR. 
80. Parallel Rules, Ebony, 6 inch 87 ets, 9 in, 62,12 in..75, 15 in. —$1,00 
80. ff « —“Tvery, 6inch, - - Tee aim 100 
30. ae ‘Brass, fine, 9 in. $1,75, 12 in. 2,50, 16 in. * 3,12 
st Ae “on rollers, 9 inch $4,25, 12 inch, ee ie fr) 
es «eo Ebony, *-12- in. 2,624 5 in 837 sae.! 4,00 
‘S “Ivory, “ . graduated edges, 12 in, “9 4,20 
18 inch, : > 2 : - . 6,00 
31. Pentagraphs of Ebony, very accurately made, - 14,00 
82 pe of Brass, » “ us Ss . 22,00 


CASES OF MATHEMATICAL DRAWING INSTRUMENTS. 


53. No. 636, Morocco ease—small German Silver Instruments— 
Needle point, 4 inch dividers, fine quality, . pe dabG 
35. No. 25, wood box, brass instruments, without needle points, 
medium quality, - - - - 1,25 
34. No. 82, wood box, brass instruments, 5 inch dividers, medium - 
quality, box scale, 4 aie - - 1,75 
ot, No. 88, wood box, brass instruments, 6 inch dividers, medium ~ 
quality, Ivory seale, - - - - sey A) 
34. No. 600, Morocco, brass instruments, common quality, box 
protractor, (fig, 22), ; - : : 1,75 
5é. No. 154, Moroéeo, German Silver instruments, fine quality, At 
Ivory protractor, (fig. 22), - - 3,50 
35. No. 054, Moroceo, German Silver instruments, with addition 
of lengthening bar, - * - ‘ $4,95 


a5 ° a ih ary . Co pve e . * 
35. No. 645, Morocco, German Silver instruments, without plain 
dividers, - - - - Coe 00 
: ~ , 


DRAWING INSTRUMENTS. Vil 

"FIGURE. PRICE, 

35. No. 023, Morocco box, brass instruments, good quality, . 2,50 
85. No. 599, do do do do common quality, box 

3 protractor, ‘ . - - : 1,25 


36. No. 786, Morocco box, German Silver instruments, fine quality 
Tyory protractor, - . - 6,50 
87, No. 745, Morocco box, German Silver instruments, fine quality, 6,50 


WL, 


a 
RY 


4 88 
88. No. 15, wood box, brass instruments, medium quality, 8,50 
ms od. do - 29, do do do needle points, med. qual. 3,75 
"39, do. 89; do do do do with bow pen, 4,25 
5 a 39. No. 40, wood box, brass instruments, needle points, with bow 
ee. si pen and proportional compasses, - - $6,00 
a : 89. No. 535, Morocco case, brass instruments, fine quality, "$50 


VIII DRAWING INSTRUMENTS, 


Prose 
L 


FIGURE. 4() > AT 

40. No, 805, wood box, German Silver Instruments, fine quality, 

40. do 535, do do do with bow pen, 
40. do 036, do do do do do and 


hair dividers, - - - 

41. do 845, wood box, German Silver instruments, fine quality, 

41, do 655, do do do with addition 

of Railroad Pen, (fig. 18) - 2 : 

41, do 455, wood box, lock and key, superior quality, without 

the proportional compasses, but with double drawing pen, 
(fig. 18) and additional pen, (fig. 17) - 

41. do 126, wood box, lock and key, German Silver instruments, 
superior quality, with addition of Railroad Pen, (fig. 18) 
and one Pen, (fig. 17) : - Sie 

do 826, Sameas No. 126, but with addition of furniture for 
Beam Compasses, (fig. 9) - - é 


41 


42. No. 5, Fish skin cases, brass instruments, box scale, - 
_ do55, do do do do Ivory seale, - 
do 57, — do do do do Ivory scale, steel joints, 


2,50 
2,75 
3,00 


“* RIGURE. PRICE, 
_ No. 1 A, Drawing Compass, joints in legs, 64 t0 7 inches long, with 
; pen, pencil-holder, needle pt,lengthening bar and dot. pen, $6,00 


No. 1 B, Drawing Compass, 6 inches long, with pen, pencil-holder, 
r lengthening bar and needle point, - - 4,75 
9, Hair Spring Divider, 5-6 inch, = - 2,00 
_* 8, Plain Divider, 44 inch, - - - 1,374 
3. do do 5-6 do - - - 1,50 
4, Uair do 44 do - - - 1,75 


5, Drawing Compass, 4 in., with pen, pencil holder and needle pt. 38,75 
- 6, The same, without the needle point, - - 3,00 


x 


SWISS INSTRUMENTS. 


FIGURE, 


. Proportional Compass, with full division for lines and circles, 


1. The same, with Micrometer Screw, - - 
‘8. Beam Compass, 19-20 inches long, in 2 German Silver bars, ' 
8. The same, 20 inches long, in 8 German Silver bars, 
8. do do 86 do do 4 do do do 
8. 1d do = 48 odo do 4 do do do 
9. Triangular Compass, ° - - 
10. Dotting Pen, - - = ee 
11. Road Pen, - - - - 
12. Pocket Divider, . - - 
8. Whole and Half Divider, - - - 


15. 
16. 
17. 
18. 
19, 
20. 
21. 


. 14 A, Universal Compass, with points to shift, - 
. 14 B, Universal Compass, with points to turn, . 


Large Steel Spring Divider, - - - 
Small Steel Stepping Divider, - - 


Small Steel Compass, with Pen, ria os - 
Drawing Pen, with joint 44 inches long, - 
do do do 54 do = = 
do do do ~ 6 do - - 


Horn Centre, with German Silver frame, : 


SWISS INSTRUMENTS. XI 
FIGURE, : PRICE. 
é 22, Bow Pen, : 4 ; : 1,80 
23. Bow Pen, with pencil holder, : ’ 2 2,50 
94, German Silver Centre, with handle, : 4 ee 
25. German Silver Paper Pins, per doz., - = 50 
25. Steel do do do - - ,60 
A No. 26, Calliper, : é ‘ - 5,00 
6: ae do English pattern, with two verniers, - 7,00 
21, Eccentric Rule, < 


ee 
28. Protractor, 44 inch diameter, whole degrees, - 1,25 

~ 28. do 5+ do half do i 1,50 
» 928. do 6 do half do - 1,62 
“98. do 64 do quarter do E 2,50 

Horn Protractors, from 25 to 2 : 2 ,50 

_ 28. Circular Protractor with arm, 8 inch diameter, quarter degrees, 8,00 
28. do do do 10% “doar do do 10,50 


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29 


Circular Protractor with vernier, 8 inch diam., quarter deg. 12,00 
do do do 10 do do 13,00 


X= SWISS INSTRUMENTS. 


FIGURE. PRICE, 


29. Half Circle Protractor with vernier, 54 inch diam., half deg. $7,50 

29. do do do 8 do quarter do 9,00 
30. Beam Compass furniture, for wood beams, - 5,00 — 
81, 88 and 34. Horn Curves, each _ - 50! 
82. Drawing Compass, 4 inches, with long ivory handle, spring, 

' and micrometer, with 2 pens, pencil holder and needle pt., 5,00 
35. Parallel Rule, with rollers, - - * 9,00 
86. Protractor Seale, divided to 4°, _ - 215 
86. - do do do 4°, - - 8,75 

A No. 87. Bow Compass, fast needle point and pen, with joints in 
both legs, - = _ 2,00. 
B No. 87. Bow See fast needle point and pencil holder, with 
joints in both leg - - - 2,00 . 
88. Lengthening ee - - - 12,00 


Persons desiring a complete Case have but to name the vehi of the N 
Instruments they want in the Box. 

The price of the Box is always according to the size and finish, 3 the. | 
same, 


Raa 4 


